ROLLOUT 6 · modelcontextprotocol/python-sdk
modelcontextprotocol__python-sdk-1864
Solved
487 stotal time
21tool calls
21model calls
5,802tokens generated
193,408prompt tokens read
Agent exceeded session timeout (7.5 min)
⚠ The request log has 21 model calls but the trace has 22 agent calls, so tokens are listed separately instead of beside each turn.
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System instructions 4,822 characters
You are a principal Python software engineer resolving a repository issue in `/workspace`. Your sole objective is to produce a minimal, root-cause source patch that passes every hidden fail-to-pass and pass-to-pass regression test on the first grading run. ## Critical Environment & Grader Rules 1. **Air-Gapped Sandbox & Available CLI Tools**: No network access. Never run `pip`, `uv`, `conda`, or `git fetch`. Note: `rg` (`ripgrep`) is NOT installed in the container — always use `grep -rn --include="*.py"` for fast exact searches so you never waste a tool call on `command not found`. 2. **Protected Grading Paths**: Before running official verification, the grading harness **strips and reverts all changes** to `tests/`, `test/`, `testing/`, `test_*.py`, `*_test.py`, `conftest.py`, `pyproject.toml`, `setup.cfg`, `pytest.ini`, and `tox.ini`. Every part of your fix MUST reside in non-test production source files. 3. **Untracked File Trap (`git add -N .`)**: `submit_patch` stages ALL untracked files inside `/workspace`! Never leave reproduction or scratch files inside `/workspace` — run reproductions inline via `python3 - <<'PY'` or inside `/tmp/repro.py` in a single `run_command`. 4. **Stdout Truncation Rule**: `run_command` truncates stdout after the first 5,000 characters from the TOP. Always run pytest quietly with short tracebacks: `pytest path/to/test_file.py -k pattern -q --tb=short --no-header` If a test file is large, redirect output to `/tmp/pytest.log` and inspect `tail -n 80 /tmp/pytest.log` so failure tracebacks at the bottom are never cut off. 5. **Strict Pacing Discipline**: `get_status` and `submit_patch` are free and do NOT count toward `max_tool_calls`. Target **16-22 counted tool calls total**, and **begin your first `edit_file` change no later than tool call 15**. Reserve at least 4 calls for verification, `git status --short && git diff`, and submission. ## Execution Protocol ### Phase 1 — Pinpoint Code & Tests Immediately (1-2 tool calls) - The user message already contains `Workspace Layout` — do NOT waste a turn running `ls` on top-level directories. - Run a single compound `run_command` with `grep -rn --include="*.py"` to locate: (a) the exact symbols, error strings, or functions from the problem description, (b) **all parallel or sibling implementations** (for example sync + async variants, `Client` + `AsyncClient`, serializer + deserializer, multiple backends/dialects, base + subclass methods, `__init__.py` / `__all__` exports), and (c) the closest existing unit test files under `tests/`. ### Phase 2 — Deep Read & Spec Anchor (2-5 tool calls) - Use `read_file` with generous `start_line` and `end_line` windows (180-300 lines per call so you read whole modules in fewer calls) on the target function/class, callers, type annotations, and neighboring tests. - Before editing, verify every explicit and implicit requirement from the issue: exact parameter names, defaults, boundary/domain edge cases, exception types/messages, `None` vs empty collection vs falsy (`0`, `False`, `""`) semantics, mutability/copying, and return types. ### Phase 3 — Reproduce Bug in One Call (1 tool call) - Run ONE concise command (`python3 - <<'PY' ... PY` or targeted `pytest ... -q --tb=short --no-header`) via `run_command` to observe the exact pre-fix failure. Do NOT spend multiple tool calls writing separate reproduction scripts. ### Phase 4 — Surgical Implementation Across All Parallel Paths (1-4 tool calls) - Begin editing by tool call 15! Use `edit_file` with 4-6 lines of exact surrounding context copied from `read_file`. - Update ALL parallel codepaths (sync/async, multiple classes/dialects, type hints) consistently so partial fixes do not fail sibling tests. - **2-Strike Edit Rule**: If `edit_file` fails twice on the same block due to whitespace or escaping, do not retry `edit_file` a third time — apply an atomic Python transformation via `run_command` and immediately verify `python3 -m py_compile path/to/file.py`. ### Phase 5 — Edge-Case Verification, Diff Hygiene & Clean Exit (2-4 tool calls) - Run a single compound `run_command` testing both your reproduction + boundary edge cases (`None`, empty input, leading/trailing delimiters, subdomain/prefix boundaries, subclass/async parity) AND the relevant existing `pytest` module(s) with `-q --tb=short --no-header`. - Run `git status --short && git diff` via `run_command`. Confirm: - ZERO untracked (`??`) files in `/workspace` (`rm -f` any untracked workspace files immediately), - ZERO modifications to `tests/` or protected config files (`git checkout -- tests/` if touched), - Minimal, clean diff with valid imports and indentation. - Call `submit_patch` once verification passes, then respond with a brief 2-sentence plain-text summary and make NO further tool calls.
Task prompt 3,632 characters
You are evaluating a software engineering task for repository modelcontextprotocol/python-sdk.
Problem Statement:
URL Parameters Not Decoded in Dynamic Resources
### Initial Checks
- [ ] I confirm that I'm using the latest version of MCP Python SDK
- [x] I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
### Description
Dynamic URL resource parameters in MCP protocol are not automatically URL-decoded, causing encoded characters (like %20 for spaces and %C3%A9 for accented characters) to be passed as-is to resource handlers instead of their decoded equivalents.
Here is a simple log for the bug:
- **before**
```
2025-06-17 14:43:44,385 [INFO] kn-graph: Found 0 products matching 'stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc' - (logger.py:226)
```
- **after explicit decode**
```
2025-06-17 14:55:10,173 [INFO] kn-graph: Found 10 products matching 'stick correcteur teinté anti-imperfections rechargeable au zinc' - (logger.py:226)
```
### Example Code
```Python
@mcp.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
"""
Find similar products based on a given product identifier.
:param product_identifier: The identifier of the product (product name or code).
:return: Similar products or an error message if none are found.
"""
print(product_identifier)
"""
-- walkaround: explicit decoding
from urllib.parse import unquote
print(unquote(product_identifier))
"""
```
### Python & MCP Python SDK
```Text
# uv pip list | grep "mcp"
mcp 1.9.2
# python --version
Python 3.13.4
```
## Task Budget (Session terminates when any budget is exhausted)
- Time allowance: 7.5 minutes
- Tool calls allowance: 30 calls
- Max loop iterations: 40 turns
## Execution Environment Rules
- Single command timeout: 90 seconds (commands exceeding this fail without ending the session)
- Command output limit: 5000 characters
- File view limit: 150 lines per read_file call
- File character limit: 10000 characters per read_file call
- Environment is offline (no network/PyPI access). All repository and test dependencies are ALREADY pre-installed. Do NOT attempt to run pip install or download packages.
## Instructions:
0. All source code is under `/workspace`. Do NOT search outside `/workspace` (e.g. `/usr/`, `/wheels/`, system site-packages). If imports fail, the issue is in the source code under `/workspace`, not in missing system packages.
1. Analyze the problem statement and any provided hints carefully to identify all requested script paths, CLI subcommands, or Python modules.
2. Inspect existing codebase conventions and test files before making edits.
3. Verify your implementation using targeted tests or inline assertions before submitting.
4. Call submit_patch only after your implementation is complete and verified.
5. As your final action, you must return a text-only response reporting your completion to terminate the session.
## Workspace Layout
The repository is located at `/workspace`. Here is the directory tree (up to 3 levels):
```
./CLAUDE.md
./CODE_OF_CONDUCT.md
./CONTRIBUTING.md
./LICENSE
./README.md
./RELEASE.md
./SECURITY.md
./docs
./examples
./mkdocs.yml
./pyproject.toml
./scripts
./scripts/test
./scripts/update_readme_snippets.py
./src
./src/mcp
./src/mcp/__init__.py
./src/mcp/cli
./src/mcp/client
./src/mcp/os
./src/mcp/py.typed
./src/mcp/server
./src/mcp/shared
./src/mcp/types.py
./tests
./uv.lock
```
Turn 1at 22 s215 tokens out3,031 prompt tokens
The user is reporting that dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded.
When a resource is defined with a template like `products://search/{product_identifier}`, the value passed to the handler for `product_identifier` is the raw URL-encoded string (e.g., `%20` instead of space).
I need to find where these resource templates are parsed and where the parameters are extracted from the URI.
Plan:
1. Search for `resource` or where resource templates are handled in `src/mcp`.
2. Identify the code that extracts parameters from the URI.
3. Implement URL decoding for these parameters.
4. Verify the fix with a reproduction script.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" -e \"resource\" src/mcp | grep \"template\" -C 5 || grep -rn --include=\"*.py\" -e \"resource\" src/mcp"
}Result of run_command 5,262 characters
{
"status": "ok",
"stdout": "src/mcp/types.py:694: \"\"\"The URI of this resource.\"\"\"\nsrc/mcp/types.py:696: \"\"\"A description of what this resource represents.\"\"\"\nsrc/mcp/types.py:698: \"\"\"The MIME type of this resource, if known.\"\"\"\nsrc/mcp/types.py:701: The size of the raw resource content, in bytes (i.e., before base64 encoding\nsrc/mcp/types.py:707: \"\"\"An optional list of icons for this resource.\"\"\"\nsrc/mcp/types.py:717: \"\"\"A template description for resources available on the server.\"\"\"\nsrc/mcp/types.py:721: A URI template (according to RFC 6570) that can be used to construct resource\nsrc/mcp/types.py:728: The MIME type for all resources that match this template. This should only be\nsrc/mcp/types.py:729: included if all resources matching this template have the same type.\nsrc/mcp/types.py:732: \"\"\"An optional list of icons for this resource template.\"\"\"\nsrc/mcp/types.py:742: \"\"\"The server's response to a resources/list request from the client.\"\"\"\nsrc/mcp/types.py:744: resources: list[Resource]\nsrc/mcp/types.py:747:class ListResourceTemplatesRequest(PaginatedRequest[Literal[\"resources/templates/list\"]]):\nsrc/mcp/types.py:748: \"\"\"Sent from the client to request a list of resource templates the server has.\"\"\"\nsrc/mcp/types.py:750: method: Literal[\"resources/templates/list\"] = \"resources/templates/list\"\nsrc/mcp/types.py:754: \"\"\"The server's response to a resources/templates/list request from the client.\"\"\"\nsrc/mcp/types.py:756: resourceTemplates: list[ResourceTemplate]\nsrc/mcp/types.py:760: \"\"\"Parameters for reading a resource.\"\"\"\nsrc/mcp/types.py:764: The URI of the resource to read. The URI can use any protocol; it is up to the\nsrc/mcp/types.py:769:class ReadResourceRequest(Request[ReadResourceRequestParams, Literal[\"resources/read\"]]):\nsrc/mcp/types.py:770: \"\"\"Sent from the client to the server, to read a specific resource URI.\"\"\"\n--\nsrc/mcp/types.py:1092: type: Literal[\"resource\"] = \"resource\"\nsrc/mcp/types.py:1093: resource: TextResourceContents | BlobResourceContents\nsrc/mcp/types.py:1104: A resource that the server is capable of reading, included in a prompt or tool call result.\nsrc/mcp/types.py:1106: Note: resource links returned by tools are not guaranteed to appear in the results of `resources/list` requests.\nsrc/mcp/types.py:1109: type: Literal[\"resource_link\"] = \"resource_link\"\nsrc/mcp/types.py:1481: \"\"\"A reference to a resource or resource template definition.\"\"\"\nsrc/mcp/types.py:1483: type: Literal[\"ref/resource\"] = \"ref/resource\"\nsrc/mcp/types.py:1485: \"\"\"The URI or URI template of the resource.\"\"\"\nsrc/mcp/server/fastmcp/resources/templates.py:12:from mcp.server.fastmcp.resources.types import FunctionResource, Resource\nsrc/mcp/server/fastmcp/resources/templates.py:24: \"\"\"A template for dynamically creating resources.\"\"\"\nsrc/mcp/server/fastmcp/resources/templates.py:27: name: str = Field(description=\"Name of the resource\")\nsrc/mcp/server/fastmcp/resources/templates.py:28: title: str | None = Field(description=\"Human-readable title of the resource\", default=None)\nsrc/mcp/server/fastmcp/resources/templates.py:29: description: str | None = Field(description=\"Description of what the resource does\")\nsrc/mcp/server/fastmcp/resources/templates.py:30: mime_type: str = Field(default=\"text/plain\", description=\"MIME type of the resource content\")\nsrc/mcp/server/fastmcp/resources/templates.py:31: icons: list[Icon] | None = Field(default=None, description=\"Optional list of icons for the resource template\")\nsrc/mcp/server/fastmcp/resources/templates.py:32: annotations: Annotations | None = Field(default=None, description=\"Optional annotations for the resource template\")\nsrc/mcp/server/fastmcp/resources/templates.py:33: meta: dict[str, Any] | None = Field(default=None, description=\"Optional metadata for this resource template\")\nsrc/mcp/server/fastmcp/resources/templates.py:94: async def create_resource(\nsrc/mcp/server/fastmcp/resources/templates.py:100: \"\"\"Create a resource from the template with the given parameters.\"\"\"\nsrc/mcp/server/fastmcp/resources/templates.py:122: raise ValueError(f\"Error creating resource from template: {e}\")\nsrc/mcp/server/fastmcp/resources/base.py:1:\"\"\"Base classes and interfaces for FastMCP resources.\"\"\"\nsrc/mcp/server/fastmcp/resources/base.py:18: \"\"\"Base class for all resources.\"\"\"\nsrc/mcp/server/fastmcp/resources/base.py:22: uri: str = Field(default=..., description=\"URI of the resource\")\nsrc/mcp/server/fastmcp/resources/base.py:23: name: str | None = Field(description=\"Name of the resource\", default=None)\nsrc/mcp/server/fastmcp/resources/base.py:24: title: str | None = Field(description=\"Human-readable title of the resource\", default=None)\n--\nsrc/mcp/server/fastmcp/resources/types.py:156: mime_type: str = Field(default=\"application/json\", description=\"MIME type of the resource content\")\nsrc/mcp/server/fastmcp/resources/types.py:167: \"\"\"A resource that lists files in a d",
"stderr": "",
"exit_code": 0
}Turn 2at 40 s171 tokens out4,958 prompt tokens
The `grep` results point to `src/mcp/server/fastmcp/resources/templates.py`.
Specifically, line 94 `create_resource` seem to be where the resource is created from a template.
The example code uses `@mcp.resource("products://search/{product_identifier}")`, which suggests a decorator in `FastMCP`. Let's look for where this decorator is defined. It's likely in `src/mcp/server/fastmcp/server.py` or similar.
Wait, the `grep` didn't show `FastMCP` class, let's search for `.resource(`.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" \"\\.resource(\" src/mcp"
}Result of run_command 446 characters
{
"status": "ok",
"stdout": "src/mcp/server/fastmcp/server.py:551: @server.resource(\"resource://my-resource\")\nsrc/mcp/server/fastmcp/server.py:555: @server.resource(\"resource://my-resource\")\nsrc/mcp/server/fastmcp/server.py:560: @server.resource(\"resource://{city}/weather\")\nsrc/mcp/server/fastmcp/server.py:564: @server.resource(\"resource://{city}/weather\")\n",
"stderr": "",
"exit_code": 0
}Turn 3at 49 s128 tokens out5,305 prompt tokens
It's in `src/mcp/server/fastmcp/server.py`. Let's examine `src/mcp/server/fastmcp/server.py` and `src/mcp/server/fastmcp/resources/templates.py`. I'll start by reading `src/mcp/server/fastmcp/server.py` around where `.resource` is defined.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/server.py",
"start_line": 400
}Result of read_file 6,215 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/server.py",
"content": " name: Optional name for the tool (defaults to function name)\n title: Optional human-readable title for the tool\n description: Optional description of what the tool does\n annotations: Optional ToolAnnotations providing additional tool information\n structured_output: Controls whether the tool's output is structured or unstructured\n - If None, auto-detects based on the function's return type annotation\n - If True, creates a structured tool (return type annotation permitting)\n - If False, unconditionally creates an unstructured tool\n \"\"\"\n self._tool_manager.add_tool(\n fn,\n name=name,\n title=title,\n description=description,\n annotations=annotations,\n icons=icons,\n meta=meta,\n structured_output=structured_output,\n )\n\n def remove_tool(self, name: str) -> None:\n \"\"\"Remove a tool from the server by name.\n\n Args:\n name: The name of the tool to remove\n\n Raises:\n ToolError: If the tool does not exist\n \"\"\"\n self._tool_manager.remove_tool(name)\n\n def tool(\n self,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n annotations: ToolAnnotations | None = None,\n icons: list[Icon] | None = None,\n meta: dict[str, Any] | None = None,\n structured_output: bool | None = None,\n ) -> Callable[[AnyFunction], AnyFunction]:\n \"\"\"Decorator to register a tool.\n\n Tools can optionally request a Context object by adding a parameter with the\n Context type annotation. The context provides access to MCP capabilities like\n logging, progress reporting, and resource access.\n\n Args:\n name: Optional name for the tool (defaults to function name)\n title: Optional human-readable title for the tool\n description: Optional description of what the tool does\n annotations: Optional ToolAnnotations providing additional tool information\n structured_output: Controls whether the tool's output is structured or unstructured\n - If None, auto-detects based on the function's return type annotation\n - If True, creates a structured tool (return type annotation permitting)\n - If False, unconditionally creates an unstructured tool\n\n Example:\n @server.tool()\n def my_tool(x: int) -> str:\n return str(x)\n\n @server.tool()\n def tool_with_context(x: int, ctx: Context) -> str:\n ctx.info(f\"Processing {x}\")\n return str(x)\n\n @server.tool()\n async def async_tool(x: int, context: Context) -> str:\n await context.report_progress(50, 100)\n return str(x)\n \"\"\"\n # Check if user passed function directly instead of calling decorator\n if callable(name):\n raise TypeError(\n \"The @tool decorator was used incorrectly. Did you forget to call it? Use @tool() instead of @tool\"\n )\n\n def decorator(fn: AnyFunction) -> AnyFunction:\n self.add_tool(\n fn,\n name=name,\n title=title,\n description=description,\n annotations=annotations,\n icons=icons,\n meta=meta,\n structured_output=structured_output,\n )\n return fn\n\n return decorator\n\n def completion(self):\n \"\"\"Decorator to register a completion handler.\n\n The completion handler receives:\n - ref: PromptReference or ResourceTemplateReference\n - argument: CompletionArgument with name and partial value\n - context: Optional CompletionContext with previously resolved arguments\n\n Example:\n @mcp.completion()\n async def handle_completion(ref, argument, context):\n if isinstance(ref, ResourceTemplateReference):\n # Return completions based on ref, argument, and context\n return Completion(values=[\"option1\", \"option2\"])\n return None\n \"\"\"\n return self._mcp_server.completion()\n\n def add_resource(self, resource: Resource) -> None:\n \"\"\"Add a resource to the server.\n\n Args:\n resource: A Resource instance to add\n \"\"\"\n self._resource_manager.add_resource(resource)\n\n def resource(\n self,\n uri: str,\n *,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n mime_type: str | None = None,\n icons: list[Icon] | None = None,\n annotations: Annotations | None = None,\n meta: dict[str, Any] | None = None,\n ) -> Callable[[AnyFunction], AnyFunction]:\n \"\"\"Decorator to register a function as a resource.\n\n The function will be called when the resource is read to generate its content.\n The function can return:\n - str for text content\n - bytes for binary content\n - other types will be converted to JSON\n\n If the URI contains parameters (e.g. \"resource://{param}\") or the function\n has parameters, it will be registered as a template resource.\n\n Args:\n uri: URI for the resource (e.g. \"resource://my-resource\" or \"resource://{param}\")\n name: Optional name for the resource\n title: Optional human-readable title for the resource\n description: Optional description of the resource\n mime_type: Optional MIME type for the resource\n meta: Optional metadata dictionary for the resource\n",
"start_line": 400,
"end_line": 549,
"total_lines": 1298,
"is_truncated": true
}Turn 4at 52 s66 tokens out6,899 prompt tokens
I need to see the rest of `resource` method in `src/mcp/server/fastmcp/server.py`.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/server.py",
"start_line": 550
}Result of read_file 5,802 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/server.py",
"content": " Example:\n @server.resource(\"resource://my-resource\")\n def get_data() -> str:\n return \"Hello, world!\"\n\n @server.resource(\"resource://my-resource\")\n async get_data() -> str:\n data = await fetch_data()\n return f\"Hello, world! {data}\"\n\n @server.resource(\"resource://{city}/weather\")\n def get_weather(city: str) -> str:\n return f\"Weather for {city}\"\n\n @server.resource(\"resource://{city}/weather\")\n async def get_weather(city: str) -> str:\n data = await fetch_weather(city)\n return f\"Weather for {city}: {data}\"\n \"\"\"\n # Check if user passed function directly instead of calling decorator\n if callable(uri):\n raise TypeError(\n \"The @resource decorator was used incorrectly. \"\n \"Did you forget to call it? Use @resource('uri') instead of @resource\"\n )\n\n def decorator(fn: AnyFunction) -> AnyFunction:\n # Check if this should be a template\n sig = inspect.signature(fn)\n has_uri_params = \"{\" in uri and \"}\" in uri\n has_func_params = bool(sig.parameters)\n\n if has_uri_params or has_func_params:\n # Check for Context parameter to exclude from validation\n context_param = find_context_parameter(fn)\n\n # Validate that URI params match function params (excluding context)\n uri_params = set(re.findall(r\"{(\\w+)}\", uri))\n # We need to remove the context_param from the resource function if\n # there is any.\n func_params = {p for p in sig.parameters.keys() if p != context_param}\n\n if uri_params != func_params:\n raise ValueError(\n f\"Mismatch between URI parameters {uri_params} and function parameters {func_params}\"\n )\n\n # Register as template\n self._resource_manager.add_template(\n fn=fn,\n uri_template=uri,\n name=name,\n title=title,\n description=description,\n mime_type=mime_type,\n icons=icons,\n annotations=annotations,\n meta=meta,\n )\n else:\n # Register as regular resource\n resource = FunctionResource.from_function(\n fn=fn,\n uri=uri,\n name=name,\n title=title,\n description=description,\n mime_type=mime_type,\n icons=icons,\n annotations=annotations,\n meta=meta,\n )\n self.add_resource(resource)\n return fn\n\n return decorator\n\n def add_prompt(self, prompt: Prompt) -> None:\n \"\"\"Add a prompt to the server.\n\n Args:\n prompt: A Prompt instance to add\n \"\"\"\n self._prompt_manager.add_prompt(prompt)\n\n def prompt(\n self,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n icons: list[Icon] | None = None,\n ) -> Callable[[AnyFunction], AnyFunction]:\n \"\"\"Decorator to register a prompt.\n\n Args:\n name: Optional name for the prompt (defaults to function name)\n title: Optional human-readable title for the prompt\n description: Optional description of what the prompt does\n\n Example:\n @server.prompt()\n def analyze_table(table_name: str) -> list[Message]:\n schema = read_table_schema(table_name)\n return [\n {\n \"role\": \"user\",\n \"content\": f\"Analyze this schema:\\n{schema}\"\n }\n ]\n\n @server.prompt()\n async def analyze_file(path: str) -> list[Message]:\n content = await read_file(path)\n return [\n {\n \"role\": \"user\",\n \"content\": {\n \"type\": \"resource\",\n \"resource\": {\n \"uri\": f\"file://{path}\",\n \"text\": content\n }\n }\n }\n ]\n \"\"\"\n # Check if user passed function directly instead of calling decorator\n if callable(name):\n raise TypeError(\n \"The @prompt decorator was used incorrectly. \"\n \"Did you forget to call it? Use @prompt() instead of @prompt\"\n )\n\n def decorator(func: AnyFunction) -> AnyFunction:\n prompt = Prompt.from_function(func, name=name, title=title, description=description, icons=icons)\n self.add_prompt(prompt)\n return func\n\n return decorator\n\n def custom_route(\n self,\n path: str,\n methods: list[str],\n name: str | None = None,\n include_in_schema: bool = True,\n ):\n \"\"\"\n Decorator to register a custom HTTP route on the FastMCP server.\n",
"start_line": 550,
"end_line": 699,
"total_lines": 1298,
"is_truncated": true
}Turn 5at 61 s111 tokens out8,321 prompt tokens
It calls `self._resource_manager.add_template`. Let's find where `_resource_manager` is and what it does. It's likely in `src/mcp/server/fastmcp/resources/manager.py` (guessing the filename) or similar. Let's list files in `src/mcp/server/fastmcp/resources/`.
TOOL CALL · run_command
{
"command": "ls src/mcp/server/fastmcp/resources/"
}Result of run_command 127 characters
{
"status": "ok",
"stdout": "__init__.py\nbase.py\nresource_manager.py\ntemplates.py\ntypes.py\n",
"stderr": "",
"exit_code": 0
}Turn 6at 65 s63 tokens out8,498 prompt tokens
It's `src/mcp/server/fastmcp/resources/resource_manager.py`. Let's read it.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/resources/resource_manager.py"
}Result of read_file 4,364 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/resource_manager.py",
"content": "\"\"\"Resource manager functionality.\"\"\"\n\nfrom __future__ import annotations\n\nfrom collections.abc import Callable\nfrom typing import TYPE_CHECKING, Any\n\nfrom pydantic import AnyUrl\n\nfrom mcp.server.fastmcp.resources.base import Resource\nfrom mcp.server.fastmcp.resources.templates import ResourceTemplate\nfrom mcp.server.fastmcp.utilities.logging import get_logger\nfrom mcp.types import Annotations, Icon\n\nif TYPE_CHECKING:\n from mcp.server.fastmcp.server import Context\n from mcp.server.session import ServerSessionT\n from mcp.shared.context import LifespanContextT, RequestT\n\nlogger = get_logger(__name__)\n\n\nclass ResourceManager:\n \"\"\"Manages FastMCP resources.\"\"\"\n\n def __init__(self, warn_on_duplicate_resources: bool = True):\n self._resources: dict[str, Resource] = {}\n self._templates: dict[str, ResourceTemplate] = {}\n self.warn_on_duplicate_resources = warn_on_duplicate_resources\n\n def add_resource(self, resource: Resource) -> Resource:\n \"\"\"Add a resource to the manager.\n\n Args:\n resource: A Resource instance to add\n\n Returns:\n The added resource. If a resource with the same URI already exists,\n returns the existing resource.\n \"\"\"\n logger.debug(\n \"Adding resource\",\n extra={\n \"uri\": resource.uri,\n \"type\": type(resource).__name__,\n \"resource_name\": resource.name,\n },\n )\n existing = self._resources.get(str(resource.uri))\n if existing:\n if self.warn_on_duplicate_resources:\n logger.warning(f\"Resource already exists: {resource.uri}\")\n return existing\n self._resources[str(resource.uri)] = resource\n return resource\n\n def add_template(\n self,\n fn: Callable[..., Any],\n uri_template: str,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n mime_type: str | None = None,\n icons: list[Icon] | None = None,\n annotations: Annotations | None = None,\n meta: dict[str, Any] | None = None,\n ) -> ResourceTemplate:\n \"\"\"Add a template from a function.\"\"\"\n template = ResourceTemplate.from_function(\n fn,\n uri_template=uri_template,\n name=name,\n title=title,\n description=description,\n mime_type=mime_type,\n icons=icons,\n annotations=annotations,\n meta=meta,\n )\n self._templates[template.uri_template] = template\n return template\n\n async def get_resource(\n self,\n uri: AnyUrl | str,\n context: Context[ServerSessionT, LifespanContextT, RequestT] | None = None,\n ) -> Resource | None:\n \"\"\"Get resource by URI, checking concrete resources first, then templates.\"\"\"\n uri_str = str(uri)\n logger.debug(\"Getting resource\", extra={\"uri\": uri_str})\n\n # First check concrete resources\n if resource := self._resources.get(uri_str):\n return resource\n\n # Then check templates\n for template in self._templates.values():\n if params := template.matches(uri_str):\n try:\n return await template.create_resource(uri_str, params, context=context)\n except Exception as e: # pragma: no cover\n raise ValueError(f\"Error creating resource from template: {e}\")\n\n raise ValueError(f\"Unknown resource: {uri}\")\n\n def list_resources(self) -> list[Resource]:\n \"\"\"List all registered resources.\"\"\"\n logger.debug(\"Listing resources\", extra={\"count\": len(self._resources)})\n return list(self._resources.values())\n\n def list_templates(self) -> list[ResourceTemplate]:\n \"\"\"List all registered templates.\"\"\"\n logger.debug(\"Listing templates\", extra={\"count\": len(self._templates)})\n return list(self._templates.values())",
"start_line": 1,
"end_line": 115,
"total_lines": 115,
"is_truncated": false
}Turn 7at 74 s143 tokens out9,732 prompt tokens
In `ResourceManager.get_resource`, it iterates over templates and calls `template.matches(uri_str)`. If it matches, it gets `params` and calls `template.create_resource(uri_str, params, context=context)`. The issue is most likely in how `params` are extracted in `ResourceTemplate.matches` or how they are used in `ResourceTemplate.create_resource`. Let's look at `src/mcp/server/fastmcp/resources/templates.py`.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py"
}Result of read_file 5,308 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": "\"\"\"Resource template functionality.\"\"\"\n\nfrom __future__ import annotations\n\nimport inspect\nimport re\nfrom collections.abc import Callable\nfrom typing import TYPE_CHECKING, Any\n\nfrom pydantic import BaseModel, Field, validate_call\n\nfrom mcp.server.fastmcp.resources.types import FunctionResource, Resource\nfrom mcp.server.fastmcp.utilities.context_injection import find_context_parameter, inject_context\nfrom mcp.server.fastmcp.utilities.func_metadata import func_metadata\nfrom mcp.types import Annotations, Icon\n\nif TYPE_CHECKING:\n from mcp.server.fastmcp.server import Context\n from mcp.server.session import ServerSessionT\n from mcp.shared.context import LifespanContextT, RequestT\n\n\nclass ResourceTemplate(BaseModel):\n \"\"\"A template for dynamically creating resources.\"\"\"\n\n uri_template: str = Field(description=\"URI template with parameters (e.g. weather://{city}/current)\")\n name: str = Field(description=\"Name of the resource\")\n title: str | None = Field(description=\"Human-readable title of the resource\", default=None)\n description: str | None = Field(description=\"Description of what the resource does\")\n mime_type: str = Field(default=\"text/plain\", description=\"MIME type of the resource content\")\n icons: list[Icon] | None = Field(default=None, description=\"Optional list of icons for the resource template\")\n annotations: Annotations | None = Field(default=None, description=\"Optional annotations for the resource template\")\n meta: dict[str, Any] | None = Field(default=None, description=\"Optional metadata for this resource template\")\n fn: Callable[..., Any] = Field(exclude=True)\n parameters: dict[str, Any] = Field(description=\"JSON schema for function parameters\")\n context_kwarg: str | None = Field(None, description=\"Name of the kwarg that should receive context\")\n\n @classmethod\n def from_function(\n cls,\n fn: Callable[..., Any],\n uri_template: str,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n mime_type: str | None = None,\n icons: list[Icon] | None = None,\n annotations: Annotations | None = None,\n meta: dict[str, Any] | None = None,\n context_kwarg: str | None = None,\n ) -> ResourceTemplate:\n \"\"\"Create a template from a function.\"\"\"\n func_name = name or fn.__name__\n if func_name == \"<lambda>\":\n raise ValueError(\"You must provide a name for lambda functions\") # pragma: no cover\n\n # Find context parameter if it exists\n if context_kwarg is None: # pragma: no branch\n context_kwarg = find_context_parameter(fn)\n\n # Get schema from func_metadata, excluding context parameter\n func_arg_metadata = func_metadata(\n fn,\n skip_names=[context_kwarg] if context_kwarg is not None else [],\n )\n parameters = func_arg_metadata.arg_model.model_json_schema()\n\n # ensure the arguments are properly cast\n fn = validate_call(fn)\n\n return cls(\n uri_template=uri_template,\n name=func_name,\n title=title,\n description=description or fn.__doc__ or \"\",\n mime_type=mime_type or \"text/plain\",\n icons=icons,\n annotations=annotations,\n meta=meta,\n fn=fn,\n parameters=parameters,\n context_kwarg=context_kwarg,\n )\n\n def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n\n async def create_resource(\n self,\n uri: str,\n params: dict[str, Any],\n context: Context[ServerSessionT, LifespanContextT, RequestT] | None = None,\n ) -> Resource:\n \"\"\"Create a resource from the template with the given parameters.\"\"\"\n try:\n # Add context to params if needed\n params = inject_context(self.fn, params, context, self.context_kwarg)\n\n # Call function and check if result is a coroutine\n result = self.fn(**params)\n if inspect.iscoroutine(result):\n result = await result\n\n return FunctionResource(\n uri=uri, # type: ignore\n name=self.name,\n title=self.title,\n description=self.description,\n mime_type=self.mime_type,\n icons=self.icons,\n annotations=self.annotations,\n meta=self.meta,\n fn=lambda: result, # Capture result in closure\n )\n except Exception as e:\n raise ValueError(f\"Error creating resource from template: {e}\")",
"start_line": 1,
"end_line": 122,
"total_lines": 122,
"is_truncated": false
}Turn 8at 124 s657 tokens out11,299 prompt tokens
The logic in `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
This extracts the parameters from the URI using regex group names. It does NOT perform any URL decoding on the extracted values.
I should use `urllib.parse.unquote` on the values in the `groupdict()`.
Wait, if I just `unquote` everything in `groupdict()`, will that be correct?
Yes, because the values in the URI are URL-encoded, and we want the decoded values to pass to the function.
Let's verify this with a reproduction script.
TOOL CALL · write_file
{
"content": "\nfrom mcp.server.fastmcp import FastMCP\nimport asyncio\nfrom urllib.parse import quote\n\nserver = FastMCP(\"repro-server\")\n\nparams_captured = {}\n\n@server.resource(\"products://search/{product_identifier}\")\ndef find_similar_products(product_identifier: str):\n params_captured[\"product_identifier\"] = product_identifier\n return f\"Found products for {product_identifier}\"\n\nasync def main():\n # Test cases\n test_cases = [\n (\"products://search/stick%20correcteur\", \"stick correcteur\"),\n (\"products://search/teint%C3%A9\", \"teinté\"),\n (\"products://search/hello%20world\", \"hello world\"),\n ]\n \n for uri, expected in test_cases:\n print(f\"Testing URI: {uri}\")\n try:\n resource = await server._resource_manager.get_resource(uri)\n # We need to call the resource's function to capture the value\n # FunctionResource.fn is a lambda that returns the result in this case\n # because create_resource calls the function and wraps it.\n # Actually, create_resource already called the function.\n # Wait, FunctionResource in FastMCP:\n # Let's check FunctionResource definition.\n except Exception as e:\n print(f\"Error getting resource: {e}\")\n\n print(f\"Captured params: {params_captured}\")\n for uri, expected in test_cases:\n # We can just check the captured params if we run them sequentially\n # but the current capture is not per-test.\n pass\n\nif __name__ == \"__main__\":\n asyncio.run(main())\n\"\"\"\n",
"filepath": "/tmp/repro.py"
}Result of write_file 136 characters
{
"status": "error",
"error_type": "FileWriteError",
"error_message": "Path traversal detected: '/tmp/repro.py' escapes workspace root."
}Turn 9at 151 s477 tokens out12,010 prompt tokens
Ah, I cannot write to `/tmp/repro.py` using `write_file`. I should use `run_command` with a python heredoc or write to a file within `/workspace`. But the rules say "Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command". Wait, the rules say: "Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command." So I should use `run_command` with `python3 - <<'PY'`. Let's try this:
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nfrom mcp.server.fastmcp import FastMCP\nimport asyncio\n\nserver = FastMCP(\"repro-server\")\n\ncaptured = []\n\n@server.resource(\"products://search/{product_identifier}\")\ndef find_similar_products(product_identifier: str):\n captured.append(product_identifier)\n return f\"Found products for {product_identifier}\"\n\nasync def main():\n tests = [\n \"products://search/stick%20correcteur\",\n \"products://search/teint%C3%A9\",\n ]\n \n for uri in tests:\n await server._resource_manager.get_resource(uri)\n \n print(f\"Captured: {captured}\")\n \n # Expected: ['stick correcteur', 'teinté']\n # Actual before fix: ['stick%20correcteur', 'teint%C3%A9']\n \n # Simple assertion to fail if not decoded\n import urllib.parse\n for val in captured:\n if \"%\" in val:\n print(f\"FAILURE: Value {val} is still encoded\")\n exit(1)\n \n print(\"SUCCESS: Values are decoded\")\n exit(0)\n\nif __name__ == \"__main__\":\n asyncio.run(main())\nPY\n"
}Result of run_command 329 characters
{
"status": "error",
"error_type": "CommandError",
"error_message": "Captured: ['stick%20correcteur', 'teint%C3%A9']\nFAILURE: Value stick%20correcteur is still encoded\n",
"details": {
"stdout": "Captured: ['stick%20correcteur', 'teint%C3%A9']\nFAILURE: Value stick%20correcteur is still encoded\n",
"stderr": "",
"exit_code": 1
}
}Turn 10at 170 s425 tokens out12,616 prompt tokens
The reproduction script confirmed the bug. Now I will apply the fix in `src/mcp/server/fastmcp/resources/templates.py` by using `urllib.parse.unquote` on the extracted parameters.
I'll modify `matches` method in `ResourceTemplate` class.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None
```
I will change it to:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n from urllib.parse import unquote\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None
```
Wait, should I import `unquote` at the top of the file? Yes, that's cleaner.
Let's check the imports in `src/mcp/server/fastmcp/resources/templates.py`.
TOOL CALL · read_file
{
"end_line": 20,
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"start_line": 1
}Result of read_file 885 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": "\"\"\"Resource template functionality.\"\"\"\n\nfrom __future__ import annotations\n\nimport inspect\nimport re\nfrom collections.abc import Callable\nfrom typing import TYPE_CHECKING, Any\n\nfrom pydantic import BaseModel, Field, validate_call\n\nfrom mcp.server.fastmcp.resources.types import FunctionResource, Resource\nfrom mcp.server.fastmcp.utilities.context_injection import find_context_parameter, inject_context\nfrom mcp.server.fastmcp.utilities.func_metadata import func_metadata\nfrom mcp.types import Annotations, Icon\n\nif TYPE_CHECKING:\n from mcp.server.fastmcp.server import Context\n from mcp.server.session import ServerSessionT\n from mcp.shared.context import LifespanContextT, RequestT",
"start_line": 1,
"end_line": 20,
"total_lines": 122,
"is_truncated": false
}Turn 11at 175 s96 tokens out13,324 prompt tokens
I'll add `from urllib.parse import unquote` and modify `matches`.
TOOL CALL · edit_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": "import inspect\nimport re\nfrom urllib.parse import unquote\nfrom collections.abc import Callable",
"old_string": "import inspect\nimport re\nfrom collections.abc import Callable"
}Result of edit_file 423 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "exact",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -4,6 +4,7 @@\n \n import inspect\n import re\n+from urllib.parse import unquote\n from collections.abc import Callable\n from typing import TYPE_CHECKING, Any\n \n",
"is_truncated": false
}Turn 12at 185 s291 tokens out13,582 prompt tokens
Now modify the `matches` method.
TOOL CALL · edit_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \\\"\\\"\\\"Check if URI matches template and extract parameters.\\\"\\\"\\\"\\n # Convert template to regex pattern\\n pattern = self.uri_template.replace(\\\"{\\\", \\\"(?P<\\\").replace(\\\"}\\\", \\\">[^/]+)\\\")\\n match = re.match(f\\\"^{pattern}$\\\", uri)\\n if match:\\n return {k: unquote(v) for k, v in match.groupdict().items()}\\n return None",
"old_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \\\"\\\"\\\"Check if URI matches template and extract parameters.\\\"\\\"\\\"\\n # Convert template to regex pattern\\n pattern = self.uri_template.replace(\\\"{\\\", \\\"(?P<\\\").replace(\\\"}\\\", \\\">[^/]+)\\\")\\n match = re.match(f\\\"^{pattern}$\\\", uri)\\n if match:\\n return match.groupdict()\\n return None"
}Result of edit_file 613 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "unescaped",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -89,7 +89,7 @@\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n",
"is_truncated": false
}Turn 13at 204 s352 tokens out14,100 prompt tokens
Now I will run the reproduction script again to verify the fix.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nfrom mcp.server.fastmcp import FastMCP\nimport asyncio\n\nserver = FastMCP(\"repro-server\")\n\ncaptured = []\n\n@server.resource(\"products://search/{product_identifier}\")\ndef find_similar_products(product_identifier: str):\n captured.append(product_identifier)\n return f\"Found products for {product_identifier}\"\n\nasync def main():\n tests = [\n \"products://search/stick%20correcteur\",\n \"products://search/teint%C3%A9\",\n ]\n \n for uri in tests:\n await server._resource_manager.get_resource(uri)\n \n print(f\"Captured: {captured}\")\n \n # Expected: ['stick correcteur', 'teinté']\n \n import urllib.parse\n for val in captured:\n if \"%\" in val:\n print(f\"FAILURE: Value {val} is still encoded\")\n exit(1)\n \n # Also check if it's actually decoded correctly\n expected = [\"stick correcteur\", \"teinté\"]\n if captured != expected:\n print(f\"FAILURE: Expected {expected}, got {captured}\")\n exit(1)\n\n print(\"SUCCESS: Values are decoded\")\n exit(0)\n\nif __name__ == \"__main__\":\n asyncio.run(main())\nPY\n"
}Result of run_command 136 characters
{
"status": "ok",
"stdout": "Captured: ['stick correcteur', 'teinté']\nSUCCESS: Values are decoded\n",
"stderr": "",
"exit_code": 0
}Turn 14at 226 s291 tokens out14,510 prompt tokens
The fix works for the reproduction script. Now I should check if there are any other places where URI parameters are extracted and not decoded.
In `src/mcp/server/fastmcp/server.py`, `resource` method registers a template.
In `src/mcp/server/fastmcp/resources/resource_manager.py`, `get_resource` calls `template.matches` and `template.create_resource`.
Is there any other resource-like thing that uses templates?
`Prompt` also uses templates? Let's check.
Looking at `src/mcp/server/fastmcp/server.py`:
```python
def prompt(
self,
name: str | None = None,
title: str | None = None,
description: str | None = None,
icons: list[Icon] | None = None,
) -> Callable[[AnyFunction], AnyFunction]:
```
Prompts seem different, they don't seem to use URIs with parameters in the same way as resources.
Let's check `src/mcp/server/fastmcp/resources/types.py` just in case.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/resources/types.py"
}Result of read_file 5,222 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/types.py",
"content": "\"\"\"Concrete resource implementations.\"\"\"\n\nimport inspect\nimport json\nfrom collections.abc import Callable\nfrom pathlib import Path\nfrom typing import Any\n\nimport anyio\nimport anyio.to_thread\nimport httpx\nimport pydantic\nimport pydantic_core\nfrom pydantic import Field, ValidationInfo, validate_call\n\nfrom mcp.server.fastmcp.resources.base import Resource\nfrom mcp.types import Annotations, Icon\n\n\nclass TextResource(Resource):\n \"\"\"A resource that reads from a string.\"\"\"\n\n text: str = Field(description=\"Text content of the resource\")\n\n async def read(self) -> str:\n \"\"\"Read the text content.\"\"\"\n return self.text # pragma: no cover\n\n\nclass BinaryResource(Resource):\n \"\"\"A resource that reads from bytes.\"\"\"\n\n data: bytes = Field(description=\"Binary content of the resource\")\n\n async def read(self) -> bytes:\n \"\"\"Read the binary content.\"\"\"\n return self.data # pragma: no cover\n\n\nclass FunctionResource(Resource):\n \"\"\"A resource that defers data loading by wrapping a function.\n\n The function is only called when the resource is read, allowing for lazy loading\n of potentially expensive data. This is particularly useful when listing resources,\n as the function won't be called until the resource is actually accessed.\n\n The function can return:\n - str for text content (default)\n - bytes for binary content\n - other types will be converted to JSON\n \"\"\"\n\n fn: Callable[[], Any] = Field(exclude=True)\n\n async def read(self) -> str | bytes:\n \"\"\"Read the resource by calling the wrapped function.\"\"\"\n try:\n # Call the function first to see if it returns a coroutine\n result = self.fn()\n # If it's a coroutine, await it\n if inspect.iscoroutine(result):\n result = await result\n\n if isinstance(result, Resource): # pragma: no cover\n return await result.read()\n elif isinstance(result, bytes):\n return result\n elif isinstance(result, str):\n return result\n else:\n return pydantic_core.to_json(result, fallback=str, indent=2).decode()\n except Exception as e:\n raise ValueError(f\"Error reading resource {self.uri}: {e}\")\n\n @classmethod\n def from_function(\n cls,\n fn: Callable[..., Any],\n uri: str,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n mime_type: str | None = None,\n icons: list[Icon] | None = None,\n annotations: Annotations | None = None,\n meta: dict[str, Any] | None = None,\n ) -> \"FunctionResource\":\n \"\"\"Create a FunctionResource from a function.\"\"\"\n func_name = name or fn.__name__\n if func_name == \"<lambda>\": # pragma: no cover\n raise ValueError(\"You must provide a name for lambda functions\")\n\n # ensure the arguments are properly cast\n fn = validate_call(fn)\n\n return cls(\n uri=uri,\n name=func_name,\n title=title,\n description=description or fn.__doc__ or \"\",\n mime_type=mime_type or \"text/plain\",\n fn=fn,\n icons=icons,\n annotations=annotations,\n meta=meta,\n )\n\n\nclass FileResource(Resource):\n \"\"\"A resource that reads from a file.\n\n Set is_binary=True to read file as binary data instead of text.\n \"\"\"\n\n path: Path = Field(description=\"Path to the file\")\n is_binary: bool = Field(\n default=False,\n description=\"Whether to read the file as binary data\",\n )\n mime_type: str = Field(\n default=\"text/plain\",\n description=\"MIME type of the resource content\",\n )\n\n @pydantic.field_validator(\"path\")\n @classmethod\n def validate_absolute_path(cls, path: Path) -> Path: # pragma: no cover\n \"\"\"Ensure path is absolute.\"\"\"\n if not path.is_absolute():\n raise ValueError(\"Path must be absolute\")\n return path\n\n @pydantic.field_validator(\"is_binary\")\n @classmethod\n def set_binary_from_mime_type(cls, is_binary: bool, info: ValidationInfo) -> bool:\n \"\"\"Set is_binary based on mime_type if not explicitly set.\"\"\"\n if is_binary:\n return True\n mime_type = info.data.get(\"mime_type\", \"text/plain\")\n return not mime_type.startswith(\"text/\")\n\n async def read(self) -> str | bytes:\n \"\"\"Read the file content.\"\"\"\n try:\n if self.is_binary:\n return await anyio.to_thread.run_sync(self.path.read_bytes)\n return await anyio.to_thread.run_sync(self.path.read_text)\n except Exception as e:\n raise ValueError(f\"Error reading file {self.path}: {e}\")\n",
"start_line": 1,
"end_line": 150,
"total_lines": 203,
"is_truncated": true
}Turn 15at 316 s507 tokens out4,939 prompt tokens
`FunctionResource` from function doesn't seem to use templates. It's a fixed URI.
Let's double check `src/mcp/server/fastmcp/resources/templates.py` for any other potential issues.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
If the `uri` itself is passed encoded, we are decoding the extracted parts.
But what if the template itself contains something that needs escaping? The current implementation is quite simple: `replace("{", "(?P<").replace("}", ">[^/]+)")`.
Wait, if the `uri_template` is `products://search/{product_identifier}`, and `uri` is `products://search/stick%20correcteur`, then `match.groupdict()` will have `{'product_identifier': 'stick%20correcteur'}`. And we decode it to `stick correcteur`. This is correct.
What if the URI has other encoded characters not in the parameters?
Example: `products://category/home%20decor/item/{id}`
Template: `products://category/{category}/item/{id}`
`uri`: `products://category/home%20decor/item/123`
`groupdict()`: `{'category': 'home%20decor', 'id': '123'}`
Decoded: `{'category': 'home decor', 'id': '123'}`.
This is also correct.
Is there any case where we SHOULD NOT decode? Usually, URI parameters are expected to be decoded before being used by the handler.
I think this fix is sufficient.
Let's check for other similar patterns in the codebase.
`grep -rn "groupdict" .`
TOOL CALL · run_command
{
"command": "grep -rn \"groupdict\" ."
}Result of run_command 185 characters
{
"status": "ok",
"stdout": "./src/mcp/server/fastmcp/resources/templates.py:92: return {k: unquote(v) for k, v in match.groupdict().items()}\n",
"stderr": "",
"exit_code": 0
}Turn 16at 323 s67 tokens out5,527 prompt tokens
Only one usage of `groupdict` in the codebase (excluding tests if any). Let's run existing tests to make sure no regressions.
TOOL CALL · run_command
{
"command": "pytest src/mcp/server/fastmcp -q --tb=short --no-header"
}Result of run_command 1,979 characters
{
"status": "error",
"error_type": "CommandError",
"error_message": "bringing up nodes...\n48 workers [0 items]\n\nscheduling tests via LoadScheduling\n\n\n\u001b[92m═══════════════════════════════ \u001b[0m\u001b[34minline-snapshot\u001b[0m\u001b[92m ════════════════════════════════\u001b[0m\nINFO: inline-snapshot was disabled because you used xdist. This means that tests\nwith snapshots will continue to run, but snapshot(x) will only return x and \ninline-snapshot will not be able to fix snapshots or generate reports.\n\n\n\u001b[33m============================ \u001b[33mno tests ran\u001b[0m\u001b[33m in 14.23s\u001b[0m\u001b[33m ============================\u001b[0m\n",
"details": {
"stdout": "bringing up nodes...\n48 workers [0 items]\n\nscheduling tests via LoadScheduling\n\n\n\u001b[92m═══════════════════════════════ \u001b[0m\u001b[34minline-snapshot\u001b[0m\u001b[92m ════════════════════════════════\u001b[0m\nINFO: inline-snapshot was disabled because you used xdist. This means that tests\nwith snapshots will continue to run, but snapshot(x) will only return x and \ninline-snapshot will not be able to fix snapshots or generate reports.\n\n\n\u001b[33m============================ \u001b[33mno tests ran\u001b[0m\u001b[33m in 14.23s\u001b[0m\u001b[33m ============================\u001b[0m\n",
"stderr": "",
"exit_code": 5
}
}Turn 17at 342 s54 tokens out6,147 prompt tokens
`pytest src/mcp/server/fastmcp` didn't find any tests. I should look for tests in `tests/` directory.
TOOL CALL · run_command
{
"command": "find tests -name \"*test*\""
}Result of run_command 4,668 characters
{
"status": "ok",
"stdout": "tests\ntests/test_examples.py\ntests/shared/test_win32_utils.py\ntests/shared/test_auth.py\ntests/shared/test_exceptions.py\ntests/shared/test_sse.py\ntests/shared/test_httpx_utils.py\ntests/shared/test_streamable_http.py\ntests/shared/test_tool_name_validation.py\ntests/shared/test_progress_notifications.py\ntests/shared/test_memory.py\ntests/shared/test_auth_utils.py\ntests/shared/test_session.py\ntests/shared/test_ws.py\ntests/cli/test_utils.py\ntests/experimental/tasks/test_request_context.py\ntests/experimental/tasks/test_capabilities.py\ntests/experimental/tasks/test_spec_compliance.py\ntests/experimental/tasks/server/test_integration.py\ntests/experimental/tasks/server/test_run_task_flow.py\ntests/experimental/tasks/server/test_server.py\ntests/experimental/tasks/server/test_context.py\ntests/experimental/tasks/server/test_store.py\ntests/experimental/tasks/server/test_task_result_handler.py\ntests/experimental/tasks/server/test_server_task_context.py\ntests/experimental/tasks/test_message_queue.py\ntests/experimental/tasks/client/test_capabilities.py\ntests/experimental/tasks/client/test_handlers.py\ntests/experimental/tasks/client/test_tasks.py\ntests/experimental/tasks/client/test_poll_task.py\ntests/experimental/tasks/test_elicitation_scenarios.py\ntests/server/fastmcp/test_integration.py\ntests/server/fastmcp/test_url_elicitation.py\ntests/server/fastmcp/test_tool_manager.py\ntests/server/fastmcp/test_url_elicitation_error_throw.py\ntests/server/fastmcp/test_title.py\ntests/server/fastmcp/resources/test_file_resources.py\ntests/server/fastmcp/resources/test_function_resources.py\ntests/server/fastmcp/resources/test_resource_manager.py\ntests/server/fastmcp/resources/test_resources.py\ntests/server/fastmcp/resources/test_resource_template.py\ntests/server/fastmcp/auth/test_auth_integration.py\ntests/server/fastmcp/test_parameter_descriptions.py\ntests/server/fastmcp/test_func_metadata.py\ntests/server/fastmcp/servers/test_file_server.py\ntests/server/fastmcp/test_elicitation.py\ntests/server/fastmcp/test_server.py\ntests/server/fastmcp/prompts/test_base.py\ntests/server/fastmcp/prompts/test_manager.py\ntests/server/test_cancel_handling.py\ntests/server/test_stateless_mode.py\ntests/server/test_streamable_http_security.py\ntests/server/test_lifespan.py\ntests/server/auth/middleware/test_bearer_auth.py\ntests/server/auth/middleware/test_auth_context.py\ntests/server/auth/test_provider.py\ntests/server/auth/test_error_handling.py\ntests/server/auth/test_protected_resource.py\ntests/server/test_lowlevel_input_validation.py\ntests/server/test_streamable_http_manager.py\ntests/server/lowlevel/test_helper_types.py\ntests/server/lowlevel/test_server_pagination.py\ntests/server/lowlevel/test_func_inspection.py\ntests/server/lowlevel/test_server_listing.py\ntests/server/test_read_resource.py\ntests/server/test_sse_security.py\ntests/server/test_lowlevel_output_validation.py\ntests/server/test_lowlevel_tool_annotations.py\ntests/server/test_stdio.py\ntests/server/test_lowlevel_exception_handling.py\ntests/server/test_session_race_condition.py\ntests/server/test_session.py\ntests/server/test_completion_with_context.py\ntests/server/test_validation.py\ntests/test_types.py\ntests/issues/test_100_tool_listing.py\ntests/issues/test_1027_win_unreachable_cleanup.py\ntests/issues/test_88_random_error.py\ntests/issues/test_176_progress_token.py\ntests/issues/test_152_resource_mime_type.py\ntests/issues/test_1754_mime_type_parameters.py\ntests/issues/test_552_windows_hang.py\ntests/issues/test_1574_resource_uri_validation.py\ntests/issues/test_malformed_input.py\ntests/issues/test_129_resource_templates.py\ntests/issues/test_1338_icons_and_metadata.py\ntests/issues/test_188_concurrency.py\ntests/issues/test_192_request_id.py\ntests/issues/test_355_type_error.py\ntests/issues/test_141_resource_templates.py\ntests/issues/test_342_base64_encoding.py\ntests/issues/test_1363_race_condition_streamable_http.py\ntests/client/test_sampling_callback.py\ntests/client/auth/extensions/test_client_credentials.py\ntests/client/test_resource_cleanup.py\ntests/client/test_list_roots_callback.py\ntests/client/test_auth.py\ntests/client/test_session_group.py\ntests/client/test_scope_bug_1630.py\ntests/client/test_config.py\ntests/client/test_output_schema_validation.py\ntests/client/test_list_methods_cursor.py\ntests/client/test_stdio.py\ntests/client/test_http_unicode.py\ntests/client/conftest.py\ntests/client/test_logging_callback.py\ntests/client/test_notification_response.py\ntests/client/test_session.py\ntests/test_helpers.py\ntests/conftest.py\n",
"stderr": "",
"exit_code": 0
}Turn 18at 344 s51 tokens out7,897 prompt tokens
I should run tests related to resources.
TOOL CALL · run_command
{
"command": "pytest tests/server/fastmcp/resources/test_resource_template.py -q --tb=short --no-header"
}Result of run_command 5,104 characters
{
"status": "ok",
"stdout": "bringing up nodes...\n48 workers [14 items]\n\nscheduling tests via LoadScheduling\n\ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_matches \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_create_resource \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_created_resources_inherit_metadata \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_from_function_with_metadata \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_annotations_in_fastmcp \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_basemodel_conversion \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_with_annotations \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_binary_resource \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_error \n[gw3]\u001b[36m [ 7%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_error \n[gw2]\u001b[36m [ 14%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_create_resource \n[gw7]\u001b[36m [ 21%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_basemodel_conversion \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_creation \n[gw0]\u001b[36m [ 28%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_creation \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_created_resources_inherit_annotations \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_text_resource \n[gw4]\u001b[36m [ 35%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_text_resource \n[gw1]\u001b[36m [ 42%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_matches \n[gw10]\u001b[36m [ 50%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_annotations_in_fastmcp \n[gw12]\u001b[36m [ 57%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_from_function_with_metadata \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_without_annotations \n[gw9]\u001b[36m [ 64%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_without_annotations \n[gw6]\u001b[36m [ 71%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_with_annotations \n[gw11]\u001b[36m [ 78%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_created_resources_inherit_annotations \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_custom_type_conversion \n[gw13]\u001b[36m [ 85%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_created_resources_inherit_metadata \n[gw5]\u001b[36m [ 92%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_binary_resource \n[gw8]\u001b[36m [100%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_custom_type_conversion \n\n\u001b[92m═══════════════════════════════ \u001b[0m\u001b[34minline-snapshot\u001b[0m\u001b[92m ════════════════════════════════\u001b[0m\nINFO: inline-snapshot was disabled because you used xdist. This means that tests\nwith snapshots will continue to run, but snapshot(x) will only return x and \ninline-snapshot will not be able to fix snapshots or generate reports.\n\n\n\n\u001b[32m============================= \u001b[32m\u001b[1m14 passed\u001b[0m\u001b[32m in 24.23s\u001b[0m\u001b[32m ==============================\u001b[0m\n",
"stderr": "",
"exit_code": 0
}Turn 19at 376 s52 tokens out9,818 prompt tokens
All tests passed. I'm confident in the fix. I'll do one final check on `git status` and `git diff`.
TOOL CALL · run_command
{
"command": "git status --short && git diff"
}Result of run_command 943 characters
{
"status": "ok",
"stdout": " M src/mcp/server/fastmcp/resources/templates.py\ndiff --git a/src/mcp/server/fastmcp/resources/templates.py b/src/mcp/server/fastmcp/resources/templates.py\nindex 89a8ceb..e993cba 100644\n--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -4,6 +4,7 @@ from __future__ import annotations\n \n import inspect\n import re\n+from urllib.parse import unquote\n from collections.abc import Callable\n from typing import TYPE_CHECKING, Any\n \n@@ -88,7 +89,7 @@ class ResourceTemplate(BaseModel):\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n",
"stderr": "",
"exit_code": 0
}Turn 20at 396 s367 tokens out10,215 prompt tokens
Wait, I just noticed that I didn't add the import `from urllib.parse import unquote` in my `edit_file` call, but it appears in the `git diff`. Let me check the `edit_file` call I made. Ah, I see, I ONLY edited the `matches` method. But the `git diff` shows `from urllib.parse import unquote` was added. How did that happen? Looking back at my `edit_file` call: ```python
Turn 21at 396 s
TOOL CALL · edit_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None",
"old_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None"
}Result of edit_file 320 characters
{
"status": "error",
"error_type": "FileEditError",
"error_message": "Failed to replace: old_string not found. Ensure you're not escaping content incorrectly and check whitespace, indentation, and context.",
"budget_warning": "Only 10 tool call(s) remaining (20/30 used). Finalize your edits and call submit_patch soon."
}Turn 22at 454 s1,218 tokens out10,680 prompt tokens
Wait, looking at the previous `edit_file` call:
```json
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None",
"old_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None"
}
```
I forgot to add the import in `edit_file`, but the `git diff` showed it?
No, wait. Let me re-read the `git diff` from the previous `run_command`.
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
Wait, I NEVER called `edit_file` to add that import. Did I?
I see what happened. I must have misinterpreted the `git diff` or something.
Let me look at the `edit_file` response:
```json
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "unescaped",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -89,7 +89,7 @@\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n"
}
```
The `edit_file` response diff DOES NOT show the import being added.
But then I ran `git status --short && git diff` and it showed:
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
This is very strange. Where did the import come from?
Wait, maybe I ran some other command? No.
Actually, let me look at the `git diff` output again.
```
M src/mcp/server/fastmcp/resources/templates.py
diff --git a/src/mcp/server/fastmcp/resources/templates.py b/src/mcp/server/fastmcp/resources/templates.py
index 89a8ceb..e993cba 100644
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
...
@@ -88,7 +89,7 @@ class ResourceTemplate(BaseModel):
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
- return match.groupdict()
+ return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
Yes, the import IS there in the `git diff`.
If it's there, then it's fine. I will just verify if the code actually imports it.
Wait, if I didn't add it, maybe it was already there?
Let's check the file.
TOOL CALL · read_file
{
"end_line": 20,
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"start_line": 1
}Result of read_file 969 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": "\"\"\"Resource template functionality.\"\"\"\n\nfrom __future__ import annotations\n\nimport inspect\nimport re\nfrom urllib.parse import unquote\nfrom collections.abc import Callable\nfrom typing import TYPE_CHECKING, Any\n\nfrom pydantic import BaseModel, Field, validate_call\n\nfrom mcp.server.fastmcp.resources.types import FunctionResource, Resource\nfrom mcp.server.fastmcp.utilities.context_injection import find_context_parameter, inject_context\nfrom mcp.server.fastmcp.utilities.func_metadata import func_metadata\nfrom mcp.types import Annotations, Icon\n\nif TYPE_CHECKING:\n from mcp.server.fastmcp.server import Context\n from mcp.server.session import ServerSessionT",
"start_line": 1,
"end_line": 20,
"total_lines": 123,
"is_truncated": false,
"budget_warning": "Only 9 tool call(s) remaining (21/30 used). Finalize your edits and call submit_patch soon."
}Model calls (not matched to turns)
Generated tokens 215 tokens · stopped: STOP
The user is reporting that dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded.
When a resource is defined with a template like `products://search/{product_identifier}`, the value passed to the handler for `product_identifier` is the raw URL-encoded string (e.g., `%20` instead of space).
I need to find where these resource templates are parsed and where the parameters are extracted from the URI.
Plan:
1. Search for `resource` or where resource templates are handled in `src/mcp`.
2. Identify the code that extracts parameters from the URI.
3. Implement URL decoding for these parameters.
4. Verify the fix with a reproduction script.<|channel>thought
The user is reporting that dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded.
When a resource is defined with a template like `products://search/{product_identifier}`, the value passed to the handler for `product_identifier` is the raw URL-encoded string (e.g., `%20` instead of space).
I need to find where these resource templates are parsed and where the parameters are extracted from the URI.
Plan:
1. Search for `resource` or where resource templates are handled in `src/mcp`.
2. Identify the code that extracts parameters from the URI.
3. Implement URL decoding for these parameters.
4. Verify the fix with a reproduction script.<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" -e "resource" src/mcp | grep "template" -C 5 || grep -rn --include="*.py" -e "resource" src/mcp<|"|>}<tool_call|><|tool_response>
Generated tokens 171 tokens · stopped: STOP
The `grep` results point to `src/mcp/server/fastmcp/resources/templates.py`.
Specifically, line 94 `create_resource` seem to be where the resource is created from a template.
The example code uses `@mcp.resource("products://search/{product_identifier}")`, which suggests a decorator in `FastMCP`. Let's look for where this decorator is defined. It's likely in `src/mcp/server/fastmcp/server.py` or similar.
Wait, the `grep` didn't show `FastMCP` class, let's search for `.resource(`.
The `grep` results point to `src/mcp/server/fastmcp/resources/templates.py`.
Specifically, line 94 `create_resource` seem to be where the resource is created from a template.
The example code uses `@mcp.resource("products://search/{product_identifier}")`, which suggests a decorator in `FastMCP`. Let's look for where this decorator is defined. It's likely in `src/mcp/server/fastmcp/server.py` or similar.
Wait, the `grep` didn't show `FastMCP` class, let's search for `.resource(`.
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" "\.resource(" src/mcp<|"|>}<tool_call|><|tool_response>
Generated tokens 128 tokens · stopped: STOP
It's in `src/mcp/server/fastmcp/server.py`. Let's examine `src/mcp/server/fastmcp/server.py` and `src/mcp/server/fastmcp/resources/templates.py`. I'll start by reading `src/mcp/server/fastmcp/server.py` around where `.resource` is defined.
It's in `src/mcp/server/fastmcp/server.py`. Let's examine `src/mcp/server/fastmcp/server.py` and `src/mcp/server/fastmcp/resources/templates.py`.
I'll start by reading `src/mcp/server/fastmcp/server.py` around where `.resource` is defined.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/server.py<|"|>,start_line:400}<tool_call|><|tool_response>
Generated tokens 66 tokens · stopped: STOP
I need to see the rest of `resource` method in `src/mcp/server/fastmcp/server.py`.
I need to see the rest of `resource` method in `src/mcp/server/fastmcp/server.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/server.py<|"|>,start_line:550}<tool_call|><|tool_response>
Generated tokens 111 tokens · stopped: STOP
It calls `self._resource_manager.add_template`. Let's find where `_resource_manager` is and what it does. It's likely in `src/mcp/server/fastmcp/resources/manager.py` (guessing the filename) or similar. Let's list files in `src/mcp/server/fastmcp/resources/`.
It calls `self._resource_manager.add_template`. Let's find where `_resource_manager` is and what it does. It's likely in `src/mcp/server/fastmcp/resources/manager.py` (guessing the filename) or similar. Let's list files in `src/mcp/server/fastmcp/resources/`.<channel|><|tool_call>call:run_command{command:<|"|>ls src/mcp/server/fastmcp/resources/<|"|>}<tool_call|><|tool_response>
Generated tokens 63 tokens · stopped: STOP
It's `src/mcp/server/fastmcp/resources/resource_manager.py`. Let's read it.
It's `src/mcp/server/fastmcp/resources/resource_manager.py`. Let's read it.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/resource_manager.py<|"|>}<tool_call|><|tool_response>
Generated tokens 143 tokens · stopped: STOP
In `ResourceManager.get_resource`, it iterates over templates and calls `template.matches(uri_str)`. If it matches, it gets `params` and calls `template.create_resource(uri_str, params, context=context)`. The issue is most likely in how `params` are extracted in `ResourceTemplate.matches` or how they are used in `ResourceTemplate.create_resource`. Let's look at `src/mcp/server/fastmcp/resources/templates.py`.
In `ResourceManager.get_resource`, it iterates over templates and calls `template.matches(uri_str)`. If it matches, it gets `params` and calls `template.create_resource(uri_str, params, context=context)`.
The issue is most likely in how `params` are extracted in `ResourceTemplate.matches` or how they are used in `ResourceTemplate.create_resource`.
Let's look at `src/mcp/server/fastmcp/resources/templates.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>}<tool_call|><|tool_response>
Generated tokens 657 tokens · stopped: STOP
The logic in `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
This extracts the parameters from the URI using regex group names. It does NOT perform any URL decoding on the extracted values.
I should use `urllib.parse.unquote` on the values in the `groupdict()`.
Wait, if I just `unquote` everything in `groupdict()`, will that be correct?
Yes, because the values in the URI are URL-encoded, and we want the decoded values to pass to the function.
Let's verify this with a reproduction script.
The logic in `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
This extracts the parameters from the URI using regex group names. It does NOT perform any URL decoding on the extracted values.
I should use `urllib.parse.unquote` on the values in the `groupdict()`.
Wait, if I just `unquote` everything in `groupdict()`, will that be correct?
Yes, because the values in the URI are URL-encoded, and we want the decoded values to pass to the function.
Let's verify this with a reproduction script.
<channel|><|tool_call>call:write_file{filepath:<|"|>/tmp/repro.py<|"|>,content:<|"|>
from mcp.server.fastmcp import FastMCP
import asyncio
from urllib.parse import quote
server = FastMCP("repro-server")
params_captured = {}
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
params_captured["product_identifier"] = product_identifier
return f"Found products for {product_identifier}"
async def main():
# Test cases
test_cases = [
("products://search/stick%20correcteur", "stick correcteur"),
("products://search/teint%C3%A9", "teinté"),
("products://search/hello%20world", "hello world"),
]
for uri, expected in test_cases:
print(f"Testing URI: {uri}")
try:
resource = await server._resource_manager.get_resource(uri)
# We need to call the resource's function to capture the value
# FunctionResource.fn is a lambda that returns the result in this case
# because create_resource calls the function and wraps it.
# Actually, create_resource already called the function.
# Wait, FunctionResource in FastMCP:
# Let's check FunctionResource definition.
except Exception as e:
print(f"Error getting resource: {e}")
print(f"Captured params: {params_captured}")
for uri, expected in test_cases:
# We can just check the captured params if we run them sequentially
# but the current capture is not per-test.
pass
if __name__ == "__main__":
asyncio.run(main())
"""
<|"|>}<tool_call|><|tool_response>
Generated tokens 477 tokens · stopped: STOP
Ah, I cannot write to `/tmp/repro.py` using `write_file`. I should use `run_command` with a python heredoc or write to a file within `/workspace`. But the rules say "Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command". Wait, the rules say: "Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command." So I should use `run_command` with `python3 - <<'PY'`. Let's try this:
Ah, I cannot write to `/tmp/repro.py` using `write_file`. I should use `run_command` with a python heredoc or write to a file within `/workspace`. But the rules say "Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command".
Wait, the rules say:
"Never leave reproduction or scratch files inside /workspace — run reproductions inline via python3 - <<'PY' or inside /tmp/repro.py in a single run_command."
So I should use `run_command` with `python3 - <<'PY'`.
Let's try this:
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
from mcp.server.fastmcp import FastMCP
import asyncio
server = FastMCP("repro-server")
captured = []
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
captured.append(product_identifier)
return f"Found products for {product_identifier}"
async def main():
tests = [
"products://search/stick%20correcteur",
"products://search/teint%C3%A9",
]
for uri in tests:
await server._resource_manager.get_resource(uri)
print(f"Captured: {captured}")
# Expected: ['stick correcteur', 'teinté']
# Actual before fix: ['stick%20correcteur', 'teint%C3%A9']
# Simple assertion to fail if not decoded
import urllib.parse
for val in captured:
if "%" in val:
print(f"FAILURE: Value {val} is still encoded")
exit(1)
print("SUCCESS: Values are decoded")
exit(0)
if __name__ == "__main__":
asyncio.run(main())
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 425 tokens · stopped: STOP
The reproduction script confirmed the bug. Now I will apply the fix in `src/mcp/server/fastmcp/resources/templates.py` by using `urllib.parse.unquote` on the extracted parameters.
I'll modify `matches` method in `ResourceTemplate` class.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None
```
I will change it to:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n from urllib.parse import unquote\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None
```
Wait, should I import `unquote` at the top of the file? Yes, that's cleaner.
Let's check the imports in `src/mcp/server/fastmcp/resources/templates.py`.
The reproduction script confirmed the bug. Now I will apply the fix in `src/mcp/server/fastmcp/resources/templates.py` by using `urllib.parse.unquote` on the extracted parameters.
I'll modify `matches` method in `ResourceTemplate` class.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None
```
I will change it to:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n from urllib.parse import unquote\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None
```
Wait, should I import `unquote` at the top of the file? Yes, that's cleaner.
Let's check the imports in `src/mcp/server/fastmcp/resources/templates.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:1,end_line:20}<tool_call|><|tool_response>
Generated tokens 96 tokens · stopped: STOP
I'll add `from urllib.parse import unquote` and modify `matches`.
I'll add `from urllib.parse import unquote` and modify `matches`.
<channel|><|tool_call>call:edit_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,new_string:<|"|>import inspect
import re
from urllib.parse import unquote
from collections.abc import Callable<|"|>,old_string:<|"|>import inspect
import re
from collections.abc import Callable<|"|>}<tool_call|><|tool_response>
Generated tokens 291 tokens · stopped: STOP
Now modify the `matches` method.
Now modify the `matches` method.
<channel|><|tool_call>call:edit_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,new_string:<|"|> def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None<|"|>,old_string:<|"|> def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None<|"|>}<tool_call|><|tool_response>
Generated tokens 352 tokens · stopped: STOP
Now I will run the reproduction script again to verify the fix.
Now I will run the reproduction script again to verify the fix.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
from mcp.server.fastmcp import FastMCP
import asyncio
server = FastMCP("repro-server")
captured = []
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
captured.append(product_identifier)
return f"Found products for {product_identifier}"
async def main():
tests = [
"products://search/stick%20correcteur",
"products://search/teint%C3%A9",
]
for uri in tests:
await server._resource_manager.get_resource(uri)
print(f"Captured: {captured}")
# Expected: ['stick correcteur', 'teinté']
import urllib.parse
for val in captured:
if "%" in val:
print(f"FAILURE: Value {val} is still encoded")
exit(1)
# Also check if it's actually decoded correctly
expected = ["stick correcteur", "teinté"]
if captured != expected:
print(f"FAILURE: Expected {expected}, got {captured}")
exit(1)
print("SUCCESS: Values are decoded")
exit(0)
if __name__ == "__main__":
asyncio.run(main())
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 291 tokens · stopped: STOP
The fix works for the reproduction script. Now I should check if there are any other places where URI parameters are extracted and not decoded.
In `src/mcp/server/fastmcp/server.py`, `resource` method registers a template.
In `src/mcp/server/fastmcp/resources/resource_manager.py`, `get_resource` calls `template.matches` and `template.create_resource`.
Is there any other resource-like thing that uses templates?
`Prompt` also uses templates? Let's check.
Looking at `src/mcp/server/fastmcp/server.py`:
```python
def prompt(
self,
name: str | None = None,
title: str | None = None,
description: str | None = None,
icons: list[Icon] | None = None,
) -> Callable[[AnyFunction], AnyFunction]:
```
Prompts seem different, they don't seem to use URIs with parameters in the same way as resources.
Let's check `src/mcp/server/fastmcp/resources/types.py` just in case.
The fix works for the reproduction script. Now I should check if there are any other places where URI parameters are extracted and not decoded.
In `src/mcp/server/fastmcp/server.py`, `resource` method registers a template.
In `src/mcp/server/fastmcp/resources/resource_manager.py`, `get_resource` calls `template.matches` and `template.create_resource`.
Is there any other resource-like thing that uses templates?
`Prompt` also uses templates? Let's check.
Looking at `src/mcp/server/fastmcp/server.py`:
```python
def prompt(
self,
name: str | None = None,
title: str | None = None,
description: str | None = None,
icons: list[Icon] | None = None,
) -> Callable[[AnyFunction], AnyFunction]:
```
Prompts seem different, they don't seem to use URIs with parameters in the same way as resources.
Let's check `src/mcp/server/fastmcp/resources/types.py` just in case.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/types.py<|"|>}<tool_call|><|tool_response>
Generated tokens 507 tokens · stopped: STOP
`FunctionResource` from function doesn't seem to use templates. It's a fixed URI.
Let's double check `src/mcp/server/fastmcp/resources/templates.py` for any other potential issues.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
If the `uri` itself is passed encoded, we are decoding the extracted parts.
But what if the template itself contains something that needs escaping? The current implementation is quite simple: `replace("{", "(?P<").replace("}", ">[^/]+)")`.
Wait, if the `uri_template` is `products://search/{product_identifier}`, and `uri` is `products://search/stick%20correcteur`, then `match.groupdict()` will have `{'product_identifier': 'stick%20correcteur'}`. And we decode it to `stick correcteur`. This is correct.
What if the URI has other encoded characters not in the parameters?
Example: `products://category/home%20decor/item/{id}`
Template: `products://category/{category}/item/{id}`
`uri`: `products://category/home%20decor/item/123`
`groupdict()`: `{'category': 'home%20decor', 'id': '123'}`
Decoded: `{'category': 'home decor', 'id': '123'}`.
This is also correct.
Is there any case where we SHOULD NOT decode? Usually, URI parameters are expected to be decoded before being used by the handler.
I think this fix is sufficient.
Let's check for other similar patterns in the codebase.
`grep -rn "groupdict" .`
`FunctionResource` from function doesn't seem to use templates. It's a fixed URI.
Let's double check `src/mcp/server/fastmcp/resources/templates.py` for any other potential issues.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
If the `uri` itself is passed encoded, we are decoding the extracted parts.
But what if the template itself contains something that needs escaping? The current implementation is quite simple: `replace("{", "(?P<").replace("}", ">[^/]+)")`.
Wait, if the `uri_template` is `products://search/{product_identifier}`, and `uri` is `products://search/stick%20correcteur`, then `match.groupdict()` will have `{'product_identifier': 'stick%20correcteur'}`. And we decode it to `stick correcteur`. This is correct.
What if the URI has other encoded characters not in the parameters?
Example: `products://category/home%20decor/item/{id}`
Template: `products://category/{category}/item/{id}`
`uri`: `products://category/home%20decor/item/123`
`groupdict()`: `{'category': 'home%20decor', 'id': '123'}`
Decoded: `{'category': 'home decor', 'id': '123'}`.
This is also correct.
Is there any case where we SHOULD NOT decode? Usually, URI parameters are expected to be decoded before being used by the handler.
I think this fix is sufficient.
Let's check for other similar patterns in the codebase.
`grep -rn "groupdict" .`
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn "groupdict" .<|"|>}<tool_call|><|tool_response>
Generated tokens 67 tokens · stopped: STOP
Only one usage of `groupdict` in the codebase (excluding tests if any). Let's run existing tests to make sure no regressions.
Only one usage of `groupdict` in the codebase (excluding tests if any).
Let's run existing tests to make sure no regressions.
<channel|><|tool_call>call:run_command{command:<|"|>pytest src/mcp/server/fastmcp -q --tb=short --no-header<|"|>}<tool_call|><|tool_response>
Generated tokens 54 tokens · stopped: STOP
`pytest src/mcp/server/fastmcp` didn't find any tests. I should look for tests in `tests/` directory.
`pytest src/mcp/server/fastmcp` didn't find any tests. I should look for tests in `tests/` directory.<channel|><|tool_call>call:run_command{command:<|"|>find tests -name "*test*"<|"|>}<tool_call|><|tool_response>
Generated tokens 51 tokens · stopped: STOP
I should run tests related to resources.
I should run tests related to resources.<channel|><|tool_call>call:run_command{command:<|"|>pytest tests/server/fastmcp/resources/test_resource_template.py -q --tb=short --no-header<|"|>}<tool_call|><|tool_response>
Generated tokens 52 tokens · stopped: STOP
All tests passed. I'm confident in the fix. I'll do one final check on `git status` and `git diff`.
All tests passed. I'm confident in the fix. I'll do one final check on `git status` and `git diff`.
<channel|><|tool_call>call:run_command{command:<|"|>git status --short && git diff<|"|>}<tool_call|><|tool_response>
Generated tokens 367 tokens · stopped: STOP
Wait, I just noticed that I didn't add the import `from urllib.parse import unquote` in my `edit_file` call, but it appears in the `git diff`.
Let me check the `edit_file` call I made.
Ah, I see, I ONLY edited the `matches` method. But the `git diff` shows `from urllib.parse import unquote` was added.
How did that happen?
Looking back at my `edit_file` call:
```python
<|tool_call>call:edit_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,new_string:<|"|> def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None<|"|>,old_string:<|"|> def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return match.groupdict()
return None<|"|>}<tool_call|><|tool_response>
Generated tokens 1,218 tokens · stopped: STOP
Wait, looking at the previous `edit_file` call:
```json
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None",
"old_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None"
}
```
I forgot to add the import in `edit_file`, but the `git diff` showed it?
No, wait. Let me re-read the `git diff` from the previous `run_command`.
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
Wait, I NEVER called `edit_file` to add that import. Did I?
I see what happened. I must have misinterpreted the `git diff` or something.
Let me look at the `edit_file` response:
```json
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "unescaped",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -89,7 +89,7 @@\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n"
}
```
The `edit_file` response diff DOES NOT show the import being added.
But then I ran `git status --short && git diff` and it showed:
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
This is very strange. Where did the import come from?
Wait, maybe I ran some other command? No.
Actually, let me look at the `git diff` output again.
```
M src/mcp/server/fastmcp/resources/templates.py
diff --git a/src/mcp/server/fastmcp/resources/templates.py b/src/mcp/server/fastmcp/resources/templates.py
index 89a8ceb..e993cba 100644
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
...
@@ -88,7 +89,7 @@ class ResourceTemplate(BaseModel):
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
- return match.groupdict()
+ return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
Yes, the import IS there in the `git diff`.
If it's there, then it's fine. I will just verify if the code actually imports it.
Wait, if I didn't add it, maybe it was already there?
Let's check the file.
Wait, looking at the previous `edit_file` call:
```json
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None",
"old_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None"
}
```
I forgot to add the import in `edit_file`, but the `git diff` showed it?
No, wait. Let me re-read the `git diff` from the previous `run_command`.
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
Wait, I NEVER called `edit_file` to add that import. Did I?
I see what happened. I must have misinterpreted the `git diff` or something.
Let me look at the `edit_file` response:
```json
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "unescaped",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -89,7 +89,7 @@\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n"
}
```
The `edit_file` response diff DOES NOT show the import being added.
But then I ran `git status --short && git diff` and it showed:
```diff
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
```
This is very strange. Where did the import come from?
Wait, maybe I ran some other command? No.
Actually, let me look at the `git diff` output again.
```
M src/mcp/server/fastmcp/resources/templates.py
diff --git a/src/mcp/server/fastmcp/resources/templates.py b/src/mcp/server/fastmcp/resources/templates.py
index 89a8ceb..e993cba 100644
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
...
@@ -88,7 +89,7 @@ class ResourceTemplate(BaseModel):
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
- return match.groupdict()
+ return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
Yes, the import IS there in the `git diff`.
If it's there, then it's fine. I will just verify if the code actually imports it.
Wait, if I didn't add it, maybe it was already there?
Let's check the file.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:1,end_line:20}<tool_call|><|tool_response>
Patch, tests and logs
Final code change Included
diff --git a/src/mcp/server/fastmcp/resources/templates.py b/src/mcp/server/fastmcp/resources/templates.py
index 89a8ceb..e993cba 100644
--- a/src/mcp/server/fastmcp/resources/templates.py
+++ b/src/mcp/server/fastmcp/resources/templates.py
@@ -4,6 +4,7 @@ from __future__ import annotations
import inspect
import re
+from urllib.parse import unquote
from collections.abc import Callable
from typing import TYPE_CHECKING, Any
@@ -88,7 +89,7 @@ class ResourceTemplate(BaseModel):
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
- return match.groupdict()
+ return {k: unquote(v) for k, v in match.groupdict().items()}
return None
async def create_resource(
Test output Included
============================= test session starts ============================== created: 48/48 workers 48 workers [12 items] scheduling tests via LoadScheduling tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode tests/issues/test_973_url_decoding.py::test_template_matches_preserves_plus_sign tests/issues/test_973_url_decoding.py::test_template_matches_decodes_space tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_exception_has_method_attribute [gw6] [ 8%] PASSED tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error [gw11] [ 16%] PASSED tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode [gw4] [ 25%] PASSED tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode [gw8] [ 33%] PASSED tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error tests/server/test_stateless_mode.py::test_elicit_url_fails_in_stateless_mode [gw9] [ 41%] PASSED tests/server/test_stateless_mode.py::test_elicit_url_fails_in_stateless_mode tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase [gw0] [ 50%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_space tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable [gw7] [ 58%] PASSED tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable [gw1] [ 66%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters [gw2] [ 75%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode [gw5] [ 83%] PASSED tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode [gw12] [ 91%] PASSED tests/server/test_stateless_mode.py::test_exception_has_method_attribute [gw3] [100%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_preserves_plus_sign ═══════════════════════════════ inline-snapshot ════════════════════════════════ INFO: inline-snapshot was disabled because you used xdist. This means that tests with snapshots will continue to run, but snapshot(x) will only return x and inline-snapshot will not be able to fix snapshots or generate reports. ==================================== PASSES ==================================== - generated xml file: /tmp/rebench-grade-43bed1c6ea9d47a5aa05a8ebe5489a4d.xml -- =========================== short test summary info ============================ PASSED tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode PASSED tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode PASSED tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode PASSED tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error PASSED tests/server/test_stateless_mode.py::test_elicit_url_fails_in_stateless_mode PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_space PASSED tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase PASSED tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode PASSED tests/server/test_stateless_mode.py::test_exception_has_method_attribute PASSED tests/issues/test_973_url_decoding.py::test_template_matches_preserves_plus_sign ============================= 12 passed in 25.48s ==============================
Test errors Included
Test report (JUnit) Included
<?xml version="1.0" encoding="utf-8"?><testsuites name="pytest tests"><testsuite name="pytest" errors="0" failures="0" skipped="0" tests="12" time="25.484" timestamp="2026-11-14T03:41:54.842998+00:00" hostname="d60984fff24c"><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_accented_characters" time="0.003" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_space" time="0.003" /><testcase classname="tests.server.test_stateless_mode" name="test_elicit_form_fails_in_stateless_mode" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_elicit_deprecated_fails_in_stateless_mode" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_list_roots_fails_in_stateless_mode" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_exception_has_method_attribute" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_stateful_mode_does_not_raise_stateless_error" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_elicit_url_fails_in_stateless_mode" time="0.002" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_complex_phrase" time="0.003" /><testcase classname="tests.server.test_stateless_mode" name="test_stateless_error_message_is_actionable" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_create_message_fails_in_stateless_mode" time="0.004" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_preserves_plus_sign" time="0.002" /></testsuite></testsuites>
Agent log Included
[ 0.0s] 📋 System Prompt: You are a principal Python software engineer resolving a repository issue in `/workspace`.
[ 0.0s] 🎯 Task Prompt: You are evaluating a software engineering task for repository
modelcontextprotocol/python-sdk.
[ 15.3s] 💭 (667 chars) "The user is reporting that dynamic URL resource parameters in the MCP Python SDK are not
being URL-decoded.
When a resou..."
[ 15.3s] 🔧 run_command grep -rn --include="*.py" -e "resource" src/mcp | grep "template" -C 5 || grep -
[ 15.3s] → src/mcp/types.py:694: """The URI of this resource."""
[ 32.7s] 💭 (485 chars) "The `grep` results point to `src/mcp/server/fastmcp/resources/templates.py`.
Specifically, line 94 `create_resource` see..."
[ 32.7s] 🔧 run_command grep -rn --include="*.py" "\.resource(" src/mcp
[ 32.7s] → src/mcp/server/fastmcp/server.py:551: @server.resource("resource://my-resource")
[ 41.4s] 💭 (240 chars) "It's in `src/mcp/server/fastmcp/server.py`. Let's examine `src/mcp/server/fastmcp/server.py`
and `src/mcp/server/fastmcp..."
[ 41.4s] 📖 read_file (src/mcp/server/fastmcp/server.py)
[ 41.5s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/server.py', 'content': ' name: Optional
name for the too…
[ 45.2s] 💭 (82 chars) "I need to see the rest of `resource` method in `src/mcp/server/fastmcp/server.py`."
[ 45.2s] 📖 read_file (src/mcp/server/fastmcp/server.py)
[ 45.2s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/server.py', 'content': ' Example:\n
@server.resou…
[ 54.2s] 💭 (259 chars) "It calls `self._resource_manager.add_template`. Let's find where `_resource_manager` is and
what it does. It's likely in..."
[ 54.2s] 🔧 run_command ls src/mcp/server/fastmcp/resources/
[ 54.2s] → __init__.py
[ 58.0s] 💭 (75 chars) "It's `src/mcp/server/fastmcp/resources/resource_manager.py`. Let's read it."
[ 58.0s] 📖 read_file (src/mcp/server/fastmcp/resources/resource_manager.py)
[ 58.1s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/resource_manager.py', 'content':
'"""Resource manager fun…
[ 67.3s] 💭 (414 chars) "In `ResourceManager.get_resource`, it iterates over templates and calls
`template.matches(uri_str)`. If it matches, it g..."
[ 67.3s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 67.3s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '"""Resource
template functiona…
[ 116.5s] 💭 (870 chars) "The logic in `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if UR..."
[ 116.5s] 📝 write_file (/tmp/repro.py, 44 lines)
[ 116.5s] ❌ {'status': 'error', 'error_type': 'FileWriteError', 'error_message': "Path traversal detected:
'/tmp/repro.py' escapes w…
[ 143.8s] 💭 (577 chars) "Ah, I cannot write to `/tmp/repro.py` using `write_file`. I should use `run_command` with a
python heredoc or write to a..."
[ 143.8s] 🔧 run_command (40 lines) python3 - <<'PY'
[ 144.8s] → error (exit 0):
[ 162.9s] 💭 (1314 chars) "The reproduction script confirmed the bug. Now I will apply the fix in
`src/mcp/server/fastmcp/resources/templates.py` b..."
[ 162.9s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 163.0s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '"""Resource
template functiona…
[ 167.8s] 💭 (65 chars) "I'll add `from urllib.parse import unquote` and modify `matches`."
[ 167.8s] ✏️ edit_file (src/mcp/server/fastmcp/resources/templates.py)
[ 168.0s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'occurrences': 1,
'strategy': 'exact', 'di…
[ 177.7s] 💭 (32 chars) "Now modify the `matches` method."
[ 177.7s] ✏️ edit_file (src/mcp/server/fastmcp/resources/templates.py)
[ 177.9s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'occurrences': 1,
'strategy': 'unescaped',…
[ 196.8s] 💭 (63 chars) "Now I will run the reproduction script again to verify the fix."
[ 196.8s] 🔧 run_command (44 lines) python3 - <<'PY'
[ 197.1s] → Captured: ['stick correcteur', 'teinté']
[ 219.0s] 💭 (914 chars) "The fix works for the reproduction script. Now I should check if there are any other places
where URI parameters are ext..."
[ 219.0s] 📖 read_file (src/mcp/server/fastmcp/resources/types.py)
[ 219.0s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/types.py', 'content': '"""Concrete
resource implementatio…
[ 308.7s] 💭 (1719 chars) "`FunctionResource` from function doesn't seem to use templates. It's a fixed URI.
Let's double check `src/mcp/server/fa..."
[ 308.7s] 🔧 run_command grep -rn "groupdict" .
[ 308.7s] → ./src/mcp/server/fastmcp/resources/templates.py:92: return {k: unquote(v) for k, v in
match.groupdict().items
[ 316.0s] 💭 (126 chars) "Only one usage of `groupdict` in the codebase (excluding tests if any).
Let's run existing tests to make sure no regres..."
[ 316.0s] 🔧 run_command pytest src/mcp/server/fastmcp -q --tb=short --no-header
[ 331.0s] → error (exit 0):
[ 334.5s] 💭 (101 chars) "`pytest src/mcp/server/fastmcp` didn't find any tests. I should look for tests in `tests/`
directory."
[ 334.5s] 🔧 run_command find tests -name "*test*"
[ 334.6s] → tests
[ 337.3s] 💭 (40 chars) "I should run tests related to resources."
[ 337.3s] 🔧 run_command pytest tests/server/fastmcp/resources/test_resource_template.py -q --tb=short --
[ 362.0s] → bringing up nodes...
[ 368.9s] 💭 (99 chars) "All tests passed. I'm confident in the fix. I'll do one final check on `git status` and `git
diff`."
[ 368.9s] 🔧 run_command git status --short && git diff
[ 368.9s] → M src/mcp/server/fastmcp/resources/templates.py
[ 389.1s] 💬 Wait, I just noticed that I didn't add the import `from urllib.parse import unquote` in my `edit_file`
call, but it appears in the `git diff`.
Let me...
[ 389.1s] ✏️ edit_file (src/mcp/server/fastmcp/resources/templates.py)
[ 389.2s] ❌ {'status': 'error', 'error_type': 'FileEditError', 'error_message': "Failed to replace: old_string not
found. Ensure you…
[ 446.8s] 💭 (3629 chars) "Wait, looking at the previous `edit_file` call:
```json
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",..."
[ 446.8s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 446.8s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '"""Resource
template functiona…
Native result row
{
"agent_error": "Agent exceeded session timeout (7.5 min)",
"duration_seconds": 486.86,
"error": "Agent exceeded session timeout (7.5 min)",
"grade": {
"collected_tests": 12,
"competition_junit_ok": true,
"error": null,
"required_issues_count": 0,
"resolved": true,
"status_counts": {
"PASSED": 12
},
"strict_clean_patch": true,
"test_exit_code": 0
},
"instance_id": "modelcontextprotocol__python-sdk-1864",
"pass_idx": 0,
"patch_chars": 802,
"phase1_seconds": 459.66,
"repo": "modelcontextprotocol/python-sdk",
"request_log_path": "/kaggle-root/working/r31/rollouts_X/requests/modelcontextprotocol__python-sdk-1864__p0__r6.jsonl",
"resolved": true,
"rollout_idx": 6,
"run_key": "modelcontextprotocol__python-sdk-1864__p0__r6",
"strict_clean_patch": true,
"tool_calls": 21,
"total_llm_calls": 21,
"trace_path": "/kaggle-root/working/r31/rollouts_X/traces/trace_modelcontextprotocol__python-sdk-1864__p0__r6.json"
}