ROLLOUT 2 · modelcontextprotocol/python-sdk
modelcontextprotocol__python-sdk-1864
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350 stotal time
23tool calls
25model calls
4,008tokens generated
212,198prompt tokens read
No error recorded
⚠ The request log has 24 model calls but the trace has 26 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 s201 tokens out3,031 prompt tokens
The objective is to fix a bug where dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded before they are passed to the handler.
Looking at the provided example:
`@mcp.resource("products://search/{product_identifier}")`
The `product_identifier` is passed as-is from the URL, so `%20` remains `%20` instead of becoming a space.
I need to find where the resource handlers are registered and where the parameters are extracted from the URI and passed to the handler.
Step 1: Locate the code responsible for resource handling and parameter extraction.
I'll search for "resource" and "uri" in `src/mcp`.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" -e \"resource\" src/mcp | grep -E \"server|types\" | head -n 20"
}Result of run_command 1,940 characters
{
"status": "ok",
"stdout": "src/mcp/shared/auth_utils.py:9:def resource_url_from_server_url(url: str | HttpUrl | AnyUrl) -> str:\nsrc/mcp/shared/auth_utils.py:10: \"\"\"Convert server URL to canonical resource URL per RFC 8707.\nsrc/mcp/types.py:394: \"\"\"Capability for resources operations.\"\"\"\nsrc/mcp/types.py:397: \"\"\"Whether this server supports subscribing to resource updates.\"\"\"\nsrc/mcp/types.py:399: \"\"\"Whether this server supports notifications for changes to the resource list.\"\"\"\nsrc/mcp/types.py:450: resources: ResourcesCapability | None = None\nsrc/mcp/types.py:451: \"\"\"Present if the server offers any resources to read.\"\"\"\nsrc/mcp/types.py:455: \"\"\"Present if the server offers autocompletion suggestions for prompts and resources.\"\"\"\nsrc/mcp/types.py:679:class ListResourcesRequest(PaginatedRequest[Literal[\"resources/list\"]]):\nsrc/mcp/types.py:680: \"\"\"Sent from the client to request a list of resources the server has.\"\"\"\nsrc/mcp/types.py:682: method: Literal[\"resources/list\"] = \"resources/list\"\nsrc/mcp/types.py:691: \"\"\"A known resource that the server is capable of reading.\"\"\"\nsrc/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\n",
"stderr": "",
"exit_code": 0
}Turn 2at 31 s106 tokens out3,894 prompt tokens
The `grep` results above show `src/mcp/types.py` and `src/mcp/shared/auth_utils.py`. But the example uses a decorator `@mcp.resource(...)`, which suggests a high-level server API. I should check `src/mcp/server` for the actual resource implementation.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" \"resource\" src/mcp/server"
}Result of run_command 5,223 characters
{
"status": "ok",
"stdout": "src/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)\nsrc/mcp/server/fastmcp/resources/base.py:25: description: str | None = Field(description=\"Description of the resource\", default=None)\nsrc/mcp/server/fastmcp/resources/base.py:28: description=\"MIME type of the resource content\",\nsrc/mcp/server/fastmcp/resources/base.py:31: icons: list[Icon] | None = Field(default=None, description=\"Optional list of icons for this resource\")\nsrc/mcp/server/fastmcp/resources/base.py:32: annotations: Annotations | None = Field(default=None, description=\"Optional annotations for the resource\")\nsrc/mcp/server/fastmcp/resources/base.py:33: meta: dict[str, Any] | None = Field(default=None, description=\"Optional metadata for this resource\")\nsrc/mcp/server/fastmcp/resources/base.py:47: \"\"\"Read the resource content.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:1:\"\"\"Concrete resource implementations.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:16:from mcp.server.fastmcp.resources.base import Resource\nsrc/mcp/server/fastmcp/resources/types.py:21: \"\"\"A resource that reads from a string.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:23: text: str = Field(description=\"Text content of the resource\")\nsrc/mcp/server/fastmcp/resources/types.py:31: \"\"\"A resource that reads from bytes.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:33: data: bytes = Field(description=\"Binary content of the resource\")\nsrc/mcp/server/fastmcp/resources/types.py:41: \"\"\"A resource that defers data loading by wrapping a function.\nsrc/mcp/server/fastmcp/resources/types.py:43: The function is only called when the resource is read, allowing for lazy loading\nsrc/mcp/server/fastmcp/resources/types.py:44: of potentially expensive data. This is particularly useful when listing resources,\nsrc/mcp/server/fastmcp/resources/types.py:45: as the function won't be called until the resource is actually accessed.\nsrc/mcp/server/fastmcp/resources/types.py:56: \"\"\"Read the resource by calling the wrapped function.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:73: raise ValueError(f\"Error reading resource {self.uri}: {e}\")\nsrc/mcp/server/fastmcp/resources/types.py:110: \"\"\"A resource that reads from a file.\nsrc/mcp/server/fastmcp/resources/types.py:122: description=\"MIME type of the resource content\",\nsrc/mcp/server/fastmcp/resources/types.py:153: \"\"\"A resource that reads from an HTTP endpoint.\"\"\"\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 directory.\"\"\"\nsrc/mcp/server/fastmcp/resources/types.py:172: mime_type: str = Field(default=\"application/json\", description=\"MIME type of the resource content\")\nsrc/mcp/server/fastmcp/resources/__init__.py:2:from .resourc",
"stderr": "",
"exit_code": 0
}Turn 3at 39 s87 tokens out5,659 prompt tokens
Wait, if the user uses `@mcp.resource("products://search/{product_identifier}")`, it looks like `FastMCP` is being used. I should check `src/mcp/server/fastmcp/server.py` if it exists.
TOOL CALL · run_command
{
"command": "find src/mcp/server/fastmcp -name \"*.py\""
}Result of run_command 893 characters
{
"status": "ok",
"stdout": "src/mcp/server/fastmcp/utilities/types.py\nsrc/mcp/server/fastmcp/utilities/context_injection.py\nsrc/mcp/server/fastmcp/utilities/__init__.py\nsrc/mcp/server/fastmcp/utilities/logging.py\nsrc/mcp/server/fastmcp/utilities/func_metadata.py\nsrc/mcp/server/fastmcp/resources/templates.py\nsrc/mcp/server/fastmcp/resources/base.py\nsrc/mcp/server/fastmcp/resources/types.py\nsrc/mcp/server/fastmcp/resources/__init__.py\nsrc/mcp/server/fastmcp/resources/resource_manager.py\nsrc/mcp/server/fastmcp/tools/base.py\nsrc/mcp/server/fastmcp/tools/tool_manager.py\nsrc/mcp/server/fastmcp/tools/__init__.py\nsrc/mcp/server/fastmcp/exceptions.py\nsrc/mcp/server/fastmcp/__init__.py\nsrc/mcp/server/fastmcp/server.py\nsrc/mcp/server/fastmcp/prompts/base.py\nsrc/mcp/server/fastmcp/prompts/__init__.py\nsrc/mcp/server/fastmcp/prompts/manager.py\n",
"stderr": "",
"exit_code": 0
}Turn 4at 43 s62 tokens out6,131 prompt tokens
Okay, `src/mcp/server/fastmcp/server.py` probably has the `@resource` decorator. Let's check it.
TOOL CALL · read_file
{
"filepath": "src/mcp/server/fastmcp/server.py"
}Result of read_file 6,368 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/server.py",
"content": "\"\"\"FastMCP - A more ergonomic interface for MCP servers.\"\"\"\n\nfrom __future__ import annotations\n\nimport inspect\nimport re\nfrom collections.abc import AsyncIterator, Awaitable, Callable, Iterable, Sequence\nfrom contextlib import AbstractAsyncContextManager, asynccontextmanager\nfrom typing import Any, Generic, Literal\n\nimport anyio\nimport pydantic_core\nfrom pydantic import BaseModel\nfrom pydantic.networks import AnyUrl\nfrom pydantic_settings import BaseSettings, SettingsConfigDict\nfrom starlette.applications import Starlette\nfrom starlette.middleware import Middleware\nfrom starlette.middleware.authentication import AuthenticationMiddleware\nfrom starlette.requests import Request\nfrom starlette.responses import Response\nfrom starlette.routing import Mount, Route\nfrom starlette.types import Receive, Scope, Send\n\nfrom mcp.server.auth.middleware.auth_context import AuthContextMiddleware\nfrom mcp.server.auth.middleware.bearer_auth import BearerAuthBackend, RequireAuthMiddleware\nfrom mcp.server.auth.provider import OAuthAuthorizationServerProvider, ProviderTokenVerifier, TokenVerifier\nfrom mcp.server.auth.settings import AuthSettings\nfrom mcp.server.elicitation import ElicitationResult, ElicitSchemaModelT, UrlElicitationResult, elicit_with_validation\nfrom mcp.server.elicitation import elicit_url as _elicit_url\nfrom mcp.server.fastmcp.exceptions import ResourceError\nfrom mcp.server.fastmcp.prompts import Prompt, PromptManager\nfrom mcp.server.fastmcp.resources import FunctionResource, Resource, ResourceManager\nfrom mcp.server.fastmcp.tools import Tool, ToolManager\nfrom mcp.server.fastmcp.utilities.context_injection import find_context_parameter\nfrom mcp.server.fastmcp.utilities.logging import configure_logging, get_logger\nfrom mcp.server.lowlevel.helper_types import ReadResourceContents\nfrom mcp.server.lowlevel.server import LifespanResultT\nfrom mcp.server.lowlevel.server import Server as MCPServer\nfrom mcp.server.lowlevel.server import lifespan as default_lifespan\nfrom mcp.server.session import ServerSession, ServerSessionT\nfrom mcp.server.sse import SseServerTransport\nfrom mcp.server.stdio import stdio_server\nfrom mcp.server.streamable_http import EventStore\nfrom mcp.server.streamable_http_manager import StreamableHTTPSessionManager\nfrom mcp.server.transport_security import TransportSecuritySettings\nfrom mcp.shared.context import LifespanContextT, RequestContext, RequestT\nfrom mcp.types import Annotations, AnyFunction, ContentBlock, GetPromptResult, Icon, ToolAnnotations\nfrom mcp.types import Prompt as MCPPrompt\nfrom mcp.types import PromptArgument as MCPPromptArgument\nfrom mcp.types import Resource as MCPResource\nfrom mcp.types import ResourceTemplate as MCPResourceTemplate\nfrom mcp.types import Tool as MCPTool\n\nlogger = get_logger(__name__)\n\n\nclass Settings(BaseSettings, Generic[LifespanResultT]):\n \"\"\"FastMCP server settings.\n\n All settings can be configured via environment variables with the prefix FASTMCP_.\n For example, FASTMCP_DEBUG=true will set debug=True.\n \"\"\"\n\n model_config = SettingsConfigDict(\n env_prefix=\"FASTMCP_\",\n env_file=\".env\",\n env_nested_delimiter=\"__\",\n nested_model_default_partial_update=True,\n extra=\"ignore\",\n )\n\n # Server settings\n debug: bool\n log_level: Literal[\"DEBUG\", \"INFO\", \"WARNING\", \"ERROR\", \"CRITICAL\"]\n\n # HTTP settings\n host: str\n port: int\n sse_path: str\n message_path: str\n streamable_http_path: str\n\n # StreamableHTTP settings\n json_response: bool\n stateless_http: bool\n \"\"\"Define if the server should create a new transport per request.\"\"\"\n\n # resource settings\n warn_on_duplicate_resources: bool\n\n # tool settings\n warn_on_duplicate_tools: bool\n\n # prompt settings\n warn_on_duplicate_prompts: bool\n\n lifespan: Callable[[FastMCP[LifespanResultT]], AbstractAsyncContextManager[LifespanResultT]] | None\n \"\"\"A async context manager that will be called when the server is started.\"\"\"\n\n auth: AuthSettings | None\n\n # Transport security settings (DNS rebinding protection)\n transport_security: TransportSecuritySettings | None\n\n\ndef lifespan_wrapper(\n app: FastMCP[LifespanResultT],\n lifespan: Callable[[FastMCP[LifespanResultT]], AbstractAsyncContextManager[LifespanResultT]],\n) -> Callable[[MCPServer[LifespanResultT, Request]], AbstractAsyncContextManager[LifespanResultT]]:\n @asynccontextmanager\n async def wrap(\n _: MCPServer[LifespanResultT, Request],\n ) -> AsyncIterator[LifespanResultT]:\n async with lifespan(app) as context:\n yield context\n\n return wrap\n\n\nclass FastMCP(Generic[LifespanResultT]):\n def __init__( # noqa: PLR0913\n self,\n name: str | None = None,\n title: str | None = None,\n description: str | None = None,\n instructions: str | None = None,\n website_url: str | None = None,\n icons: list[Icon] | None = None,\n version: str | None = None,\n auth_server_provider: (OAuthAuthorizationServerProvider[Any, Any, Any] | None) = None,\n token_verifier: TokenVerifier | None = None,\n event_store: EventStore | None = None,\n retry_interval: int | None = None,\n *,\n tools: list[Tool] | None = None,\n debug: bool = False,\n log_level: Literal[\"DEBUG\", \"INFO\", \"WARNING\", \"ERROR\", \"CRITICAL\"] = \"INFO\",\n host: str = \"127.0.0.1\",\n port: int = 8000,\n sse_path: str = \"/sse\",\n message_path: str = \"/messages/\",\n streamable_http_path: str = \"/mcp\",\n json_response: bool = False,\n stateless_http: bool = False,\n warn_on_duplicate_resources: bool = True,\n warn_on_duplicate_tools: bool = True,\n warn_on_duplicate_prompts: bool = True,\n lifespan: (Callable[[FastMCP[LifespanResultT]], AbstractAsyncContextManager[LifespanResultT]] | None) = None,\n auth: AuthSettings | None = None,\n transport_security: TransportSecuritySettings | None = None,",
"start_line": 1,
"end_line": 150,
"total_lines": 1298,
"is_truncated": true
}Turn 5at 49 s72 tokens out8,018 prompt tokens
I need to find the `resource` method in `FastMCP`. Let me read more of `src/mcp/server/fastmcp/server.py`.
TOOL CALL · run_command
{
"command": "grep -n \"def resource\" src/mcp/server/fastmcp/server.py"
}Result of run_command 83 characters
{
"status": "ok",
"stdout": "519: def resource(\n",
"stderr": "",
"exit_code": 0
}Turn 6at 53 s58 tokens out8,137 prompt tokens
Now I'll read around line 519.
TOOL CALL · read_file
{
"end_line": 600,
"filepath": "src/mcp/server/fastmcp/server.py",
"start_line": 510
}Result of read_file 3,932 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/server.py",
"content": "\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\n 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,",
"start_line": 510,
"end_line": 600,
"total_lines": 1298,
"is_truncated": false
}Turn 7at 58 s80 tokens out9,188 prompt tokens
The `resource` decorator calls `self._resource_manager.add_template`. Let's look at `ResourceManager` in `src/mcp/server/fastmcp/resources/resource_manager.py`.
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 8at 70 s200 tokens out10,439 prompt tokens
In `ResourceManager.get_resource`:
```python
# Then check templates
for template in self._templates.values():
if params := template.matches(uri_str):
try:
return await template.create_resource(uri_str, params, context=context)
except Exception as e: # pragma: no cover
raise ValueError(f\"Error creating resource from template: {e}\")
```
It calls `template.matches(uri_str)` and then `template.create_resource(uri_str, params, context=context)`.
The `params` are likely extracted in `template.matches`.
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}$\", uri)\n if match:\n return match.groupdict()\n return None\n\n async def create_resource(\n self,\n uri: str,\n params: dict[str, Any],\n context: Context[ServerSessionT, LifespanContextT, RequestT] | None = None,\n ) -> Resource:\n \"\"\"Create a resource from the template with the given parameters.\"\"\"\n try:\n # Add context to params if needed\n params = inject_context(self.fn, params, context, self.context_kwarg)\n\n # Call function and check if result is a coroutine\n result = self.fn(**params)\n if inspect.iscoroutine(result):\n result = await result\n\n return FunctionResource(\n uri=uri, # type: ignore\n name=self.name,\n title=self.title,\n description=self.description,\n mime_type=self.mime_type,\n icons=self.icons,\n annotations=self.annotations,\n meta=self.meta,\n fn=lambda: result, # Capture result in closure\n )\n except Exception as e:\n raise ValueError(f\"Error creating resource from template: {e}\")",
"start_line": 1,
"end_line": 122,
"total_lines": 122,
"is_truncated": false
}Turn 9at 109 s587 tokens out12,063 prompt tokens
Found it! In `ResourceTemplate.matches`:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
The `match.groupdict()` returns the captured groups from the URI as-is. These are URL-encoded if they contain special characters. I need to `unquote` these values.
Wait, I should check if `unquote` is already used anywhere or if I should use `urllib.parse.unquote`.
Let's create a reproduction script to confirm this.
TOOL CALL · write_file
{
"content": "\nimport asyncio\nfrom mcp.server.fastmcp.server import FastMCP\nfrom mcp.server.fastmcp.resources.resource_manager import ResourceManager\nfrom mcp.server.fastmcp.resources.templates import ResourceTemplate\nfrom urllib.parse import quote\n\nasync def test_resource_decoding():\n server = FastMCP(\"test-server\")\n\n @server.resource(\"products://search/{product_identifier}\")\n def find_similar_products(product_identifier: str):\n return product_identifier\n\n # Simulate a request for a resource with encoded characters\n # \"stick correcteur teinté anti-imperfections rechargeable au zinc\"\n product_name = \"stick correcteur teinté anti-imperfections rechargeable au zinc\"\n encoded_name = quote(product_name)\n uri = f\"products://search/{encoded_name}\"\n \n print(f\"Requesting URI: {uri}\")\n \n resource = await server._resource_manager.get_resource(uri)\n if resource:\n # FunctionResource stores the result of the function in a lambda\n result = resource.read()\n if asyncio.iscoroutine(result):\n result = asyncio.run(result)\n # But wait, FunctionResource.read() might be different.\n # Let's look at how FunctionResource is implemented.\n print(f\"Result: {result}\")\n else:\n print(\"Resource not found\")\n\nif __name__ == \"__main__\":\n asyncio.run(test_resource_decoding())\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 10at 116 s90 tokens out12,704 prompt tokens
Ah, I cannot write to `/tmp`. I must write within `/workspace` and then delete it, or use `python3 - <<'PY'`. Wait, I should check `FunctionResource`'s `read` method first to make sure I'm testing it correctly.
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 11at 130 s311 tokens out14,259 prompt tokens
Now I will run the reproduction using `python3 - <<'PY'`.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport asyncio\nfrom mcp.server.fastmcp.server import FastMCP\nfrom urllib.parse import quote\n\nasync def test_resource_decoding():\n server = FastMCP(\"test-server\")\n\n @server.resource(\"products://search/{product_identifier}\")\n def find_similar_products(product_identifier: str):\n return product_identifier\n\n product_name = \"stick correcteur teinté anti-imperfections rechargeable au zinc\"\n encoded_name = quote(product_name)\n uri = f\"products://search/{encoded_name}\"\n \n print(f\"Requesting URI: {uri}\")\n \n resource = await server._resource_manager.get_resource(uri)\n if resource:\n result = await resource.read()\n print(f\"Result: {result}\")\n if result == product_name:\n print(\"SUCCESS: Parameters were decoded\")\n else:\n print(f\"FAILURE: Parameters were not decoded. Expected '{product_name}', got '{result}'\")\n else:\n print(\"Resource not found\")\n\nif __name__ == \"__main__\":\n asyncio.run(test_resource_decoding())\nPY\n"
}Result of run_command 473 characters
{
"status": "ok",
"stdout": "Requesting URI: products://search/stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc\nResult: stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc\nFAILURE: Parameters were not decoded. Expected 'stick correcteur teinté anti-imperfections rechargeable au zinc', got 'stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc'\n",
"stderr": "",
"exit_code": 0
}Turn 12at 148 s412 tokens out14,762 prompt tokens
The reproduction confirmed the bug. Now I need to fix it in `src/mcp/server/fastmcp/resources/templates.py`.
I will import `unquote` from `urllib.parse` and apply it to the values in `match.groupdict()`.
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
I should change it to something like:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n params = match.groupdict()\n return {k: unquote(v) for k, v in params.items()}\n return None\n```
Wait, I need to make sure `unquote` is imported.
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 13at 201 s93 tokens out5,032 prompt tokens
I need to add `from urllib.parse import unquote`. Now I will apply the fix.
TOOL CALL · edit_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": "import re\nfrom urllib.parse import unquote\nfrom collections.abc import Callable",
"old_string": "import 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 14at 205 s74 tokens out5,287 prompt tokens
Now I will update the `matches` method. First I need to read the `matches` method's exact content.
TOOL CALL · read_file
{
"end_line": 122,
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"start_line": 100
}Result of read_file 1,074 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": " ) -> 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:",
"start_line": 100,
"end_line": 122,
"total_lines": 123,
"is_truncated": false
}Turn 15at 210 s62 tokens out5,653 prompt tokens
I read the wrong part of the file. I need the `matches` method.
TOOL CALL · read_file
{
"end_line": 80,
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"start_line": 50
}Result of read_file 1,374 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": " 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,",
"start_line": 50,
"end_line": 80,
"total_lines": 123,
"is_truncated": false
}Turn 16at 215 s60 tokens out6,117 prompt tokens
Still not there. Let me read from line 81.
TOOL CALL · read_file
{
"end_line": 110,
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"start_line": 81
}Result of read_file 1,301 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"content": " 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}$\", uri)\n if match:\n return match.groupdict()\n return None\n\n async def create_resource(\n self,\n uri: str,\n params: dict[str, Any],\n context: Context[ServerSessionT, LifespanContextT, RequestT] | None = None,\n ) -> Resource:\n \"\"\"Create a resource from the template with the given parameters.\"\"\"\n try:\n # Add context to params if needed\n params = inject_context(self.fn, params, context, self.context_kwarg)\n\n # Call function and check if result is a coroutine\n result = self.fn(**params)\n if inspect.iscoroutine(result):\n result = await result\n",
"start_line": 81,
"end_line": 110,
"total_lines": 123,
"is_truncated": false
}Turn 17at 235 s526 tokens out6,561 prompt tokens
Now I have the `matches` method.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
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}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n```
TOOL CALL · edit_file
{
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"new_string": " def matches(self, uri: str) -> dict[str, Any] | None:\n \"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", 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}$\", uri)\n if match:\n return match.groupdict()\n return None"
}Result of edit_file 609 characters
{
"status": "ok",
"filepath": "src/mcp/server/fastmcp/resources/templates.py",
"occurrences": 1,
"strategy": "exact",
"diff": "--- a/src/mcp/server/fastmcp/resources/templates.py\n+++ b/src/mcp/server/fastmcp/resources/templates.py\n@@ -89,7 +89,7 @@\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", 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 18at 243 s308 tokens out7,312 prompt tokens
Now I will run the reproduction script again to verify the fix.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport asyncio\nfrom mcp.server.fastmcp.server import FastMCP\nfrom urllib.parse import quote\n\nasync def test_resource_decoding():\n server = FastMCP(\"test-server\")\n\n @server.resource(\"products://search/{product_identifier}\")\n def find_similar_products(product_identifier: str):\n return product_identifier\n\n product_name = \"stick correcteur teinté anti-imperfections rechargeable au zinc\"\n encoded_name = quote(product_name)\n uri = f\"products://search/{encoded_name}\"\n \n print(f\"Requesting URI: {uri}\")\n \n resource = await server._resource_manager.get_resource(uri)\n if resource:\n result = await resource.read()\n print(f\"Result: {result}\")\n if result == product_name:\n print(\"SUCCESS: Parameters were decoded\")\n else:\n print(f\"FAILURE: Parameters were not decoded. Expected '{product_name}', got '{result}'\")\n else:\n print(\"Resource not found\")\n\nif __name__ == \"__main__\":\n asyncio.run(test_resource_decoding())\nPY\n"
}Result of run_command 288 characters
{
"status": "ok",
"stdout": "Requesting URI: products://search/stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc\nResult: stick correcteur teinté anti-imperfections rechargeable au zinc\nSUCCESS: Parameters were decoded\n",
"stderr": "",
"exit_code": 0
}Turn 19at 252 s77 tokens out7,729 prompt tokens
The reproduction script now passes. I should also check if there are any existing tests that I should run to make sure I didn't break anything. I'll search for tests related to resources.
TOOL CALL · run_command
{
"command": "grep -rn \"Resource\" tests/ | grep \"test_\" | head -n 20"
}Result of run_command 1,965 characters
{
"status": "ok",
"stdout": "tests/test_examples.py:14:from mcp.types import TextContent, TextResourceContents\ntests/test_examples.py:90: assert isinstance(content, TextResourceContents)\ntests/shared/test_sse.py:35: ReadResourceResult,\ntests/shared/test_sse.py:38: TextResourceContents,\ntests/shared/test_sse.py:260: assert isinstance(response.contents[0], TextResourceContents)\ntests/shared/test_sse.py:282: assert isinstance(response, ReadResourceResult)\ntests/shared/test_sse.py:542:# ResourceWarning filter: When mocking aconnect_sse, the sse_client's internal task\ntests/shared/test_sse.py:547:@pytest.mark.filterwarnings(\"ignore::ResourceWarning\")\ntests/shared/test_streamable_http.py:55: TextResourceContents,\ntests/shared/test_streamable_http.py:1016: assert isinstance(response.contents[0], TextResourceContents)\ntests/shared/test_streamable_http.py:1066: assert isinstance(resource.contents[0], TextResourceContents) is True\ntests/shared/test_streamable_http.py:1068: assert isinstance(content, TextResourceContents)\ntests/shared/test_streamable_http.py:1130: # Verify the notification is a ResourceUpdatedNotification\ntests/shared/test_streamable_http.py:1133: if isinstance(notif.root, types.ResourceUpdatedNotification): # pragma: no branch\ntests/shared/test_streamable_http.py:1137: assert resource_update_found, \"ResourceUpdatedNotification not received via GET stream\"\ntests/shared/test_streamable_http.py:1729: \"\"\"Client that triggers ClosedResourceError\"\"\"\ntests/shared/test_streamable_http.py:2211: if isinstance(message.root, types.ResourceUpdatedNotification): # pragma: no branch\ntests/shared/test_memory.py:7:from mcp.types import EmptyResult, Resource\ntests/shared/test_memory.py:17: Resource(\ntests/shared/test_memory.py:19: name=\"Test Resource\",\n",
"stderr": "",
"exit_code": 0
}Turn 20at 255 s52 tokens out8,412 prompt tokens
These don't seem to be FastMCP specific tests. Let me look for `fastmcp` in `tests/`.
TOOL CALL · run_command
{
"command": "find tests/ -name \"*fastmcp*\""
}Result of run_command 196 characters
{
"status": "ok",
"stdout": "tests/server/fastmcp\n",
"stderr": "",
"exit_code": 0,
"budget_warning": "Only 10 tool call(s) remaining (20/30 used). Finalize your edits and call submit_patch soon."
}Turn 21at 258 s48 tokens out8,547 prompt tokens
Okay, let's see what's in `tests/server/fastmcp`.
TOOL CALL · run_command
{
"command": "find tests/server/fastmcp -name \"*.py\""
}Result of run_command 1,245 characters
{
"status": "ok",
"stdout": "tests/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/__init__.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/auth/__init__.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/servers/__init__.py\ntests/server/fastmcp/test_elicitation.py\ntests/server/fastmcp/test_server.py\ntests/server/fastmcp/__init__.py\ntests/server/fastmcp/prompts/test_base.py\ntests/server/fastmcp/prompts/test_manager.py\ntests/server/fastmcp/prompts/__init__.py\n",
"stderr": "",
"exit_code": 0,
"budget_warning": "Only 9 tool call(s) remaining (21/30 used). Finalize your edits and call submit_patch soon."
}Turn 22at 261 s69 tokens out9,061 prompt tokens
`tests/server/fastmcp/resources/test_resource_template.py` seems exactly what I need.
TOOL CALL · run_command
{
"command": "pytest tests/server/fastmcp/resources/test_resource_template.py -q --tb=short --no-header"
}Result of run_command 5,217 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_error \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_creation \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_matches \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_created_resources_inherit_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_custom_type_conversion \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_without_annotations \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_created_resources_inherit_annotations \n[gw11]\u001b[36m [ 7%] \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_create_resource \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_text_resource \n[gw2]\u001b[36m [ 14%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_error \n[gw0]\u001b[36m [ 21%] \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::TestResourceTemplate::test_async_binary_resource \n[gw6]\u001b[36m [ 28%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_binary_resource \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_with_annotations \n[gw8]\u001b[36m [ 35%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_with_annotations \n[gw4]\u001b[36m [ 42%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_async_text_resource \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_basemodel_conversion \n[gw5]\u001b[36m [ 50%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_basemodel_conversion \n[gw9]\u001b[36m [ 57%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_without_annotations \n[gw3]\u001b[36m [ 64%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_create_resource \n[gw7]\u001b[36m [ 71%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_custom_type_conversion \ntests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_from_function_with_metadata \n[gw13]\u001b[36m [ 78%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateMetadata::test_template_from_function_with_metadata \n[gw12]\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[gw1]\u001b[36m [ 92%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplate::test_template_matches \n[gw10]\u001b[36m [100%] \u001b[0m\u001b[32mPASSED\u001b[0m tests/server/fastmcp/resources/test_resource_template.py::TestResourceTemplateAnnotations::test_template_annotations_in_fastmcp \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 24.59s\u001b[0m\u001b[32m ==============================\u001b[0m\n",
"stderr": "",
"exit_code": 0,
"budget_warning": "Only 8 tool call(s) remaining (22/30 used). Finalize your edits and call submit_patch soon."
}Turn 23at 292 s47 tokens out11,034 prompt tokens
All tests passed. I'll double check `git status --short` and `git diff` before submitting.
TOOL CALL · run_command
{
"command": "git status --short && git diff"
}Result of run_command 1,056 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}$\", uri)\n if match:\n- return match.groupdict()\n+ return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n \n async def create_resource(\n",
"stderr": "",
"exit_code": 0,
"budget_warning": "Only 7 tool call(s) remaining (23/30 used). Finalize your edits and call submit_patch soon."
}Turn 24at 305 s207 tokens out11,461 prompt tokens
The diff looks correct. I've added the `unquote` import and used it in `matches` to decode the extracted parameters.
I'll do one final check of the `ResourceTemplate.matches` method to make sure no other place needs this.
The current implementation of `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
This looks correct.
I am ready to submit.
TOOL CALL · submit_patch
Result of submit_patch 55 characters
{
"status": "ok",
"patch_size": 802,
"files_changed": 1
}Turn 25at 321 s119 tokens out11,707 prompt tokens
I have fixed the bug where dynamic URL resource parameters in `FastMCP` were not being URL-decoded. I added `urllib.parse.unquote` to the `ResourceTemplate.matches` method to ensure that parameters extracted from the URI are properly decoded before being passed to the resource handler.
Turn 26at 321 s
The bug was caused by `ResourceTemplate.matches` extracting URI parameters using `match.groupdict()` without URL-decoding them. I imported `unquote` from `urllib.parse` and updated the `matches` method to decode all extracted parameter values.
Model calls (not matched to turns)
Generated tokens 201 tokens · stopped: STOP
The objective is to fix a bug where dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded before they are passed to the handler.
Looking at the provided example:
`@mcp.resource("products://search/{product_identifier}")`
The `product_identifier` is passed as-is from the URL, so `%20` remains `%20` instead of becoming a space.
I need to find where the resource handlers are registered and where the parameters are extracted from the URI and passed to the handler.
Step 1: Locate the code responsible for resource handling and parameter extraction.
I'll search for "resource" and "uri" in `src/mcp`.<|channel>thought
The objective is to fix a bug where dynamic URL resource parameters in the MCP Python SDK are not being URL-decoded before they are passed to the handler.
Looking at the provided example:
`@mcp.resource("products://search/{product_identifier}")`
The `product_identifier` is passed as-is from the URL, so `%20` remains `%20` instead of becoming a space.
I need to find where the resource handlers are registered and where the parameters are extracted from the URI and passed to the handler.
Step 1: Locate the code responsible for resource handling and parameter extraction.
I'll search for "resource" and "uri" in `src/mcp`.<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" -e "resource" src/mcp | grep -E "server|types" | head -n 20<|"|>}<tool_call|><|tool_response>
Generated tokens 106 tokens · stopped: STOP
The `grep` results above show `src/mcp/types.py` and `src/mcp/shared/auth_utils.py`. But the example uses a decorator `@mcp.resource(...)`, which suggests a high-level server API. I should check `src/mcp/server` for the actual resource implementation.
The `grep` results above show `src/mcp/types.py` and `src/mcp/shared/auth_utils.py`. But the example uses a decorator `@mcp.resource(...)`, which suggests a high-level server API.
I should check `src/mcp/server` for the actual resource implementation.
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" "resource" src/mcp/server<|"|>}<tool_call|><|tool_response>
Generated tokens 87 tokens · stopped: STOP
Wait, if the user uses `@mcp.resource("products://search/{product_identifier}")`, it looks like `FastMCP` is being used. I should check `src/mcp/server/fastmcp/server.py` if it exists.
Wait, if the user uses `@mcp.resource("products://search/{product_identifier}")`, it looks like `FastMCP` is being used. I should check `src/mcp/server/fastmcp/server.py` if it exists.
<channel|><|tool_call>call:run_command{command:<|"|>find src/mcp/server/fastmcp -name "*.py"<|"|>}<tool_call|><|tool_response>
Generated tokens 62 tokens · stopped: STOP
Okay, `src/mcp/server/fastmcp/server.py` probably has the `@resource` decorator. Let's check it.
Okay, `src/mcp/server/fastmcp/server.py` probably has the `@resource` decorator. Let's check it.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/server.py<|"|>}<tool_call|><|tool_response>
Generated tokens 72 tokens · stopped: STOP
I need to find the `resource` method in `FastMCP`. Let me read more of `src/mcp/server/fastmcp/server.py`.
I need to find the `resource` method in `FastMCP`. Let me read more of `src/mcp/server/fastmcp/server.py`.
<channel|><|tool_call>call:run_command{command:<|"|>grep -n "def resource" src/mcp/server/fastmcp/server.py<|"|>}<tool_call|><|tool_response>
Generated tokens 58 tokens · stopped: STOP
Now I'll read around line 519.
Now I'll read around line 519.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/server.py<|"|>,end_line:600,start_line:510}<tool_call|><|tool_response>
Generated tokens 80 tokens · stopped: STOP
The `resource` decorator calls `self._resource_manager.add_template`. Let's look at `ResourceManager` in `src/mcp/server/fastmcp/resources/resource_manager.py`.
The `resource` decorator calls `self._resource_manager.add_template`. Let's look at `ResourceManager` in `src/mcp/server/fastmcp/resources/resource_manager.py`.
<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/resource_manager.py<|"|>}<tool_call|><|tool_response>
Generated tokens 200 tokens · stopped: STOP
In `ResourceManager.get_resource`:
```python
# Then check templates
for template in self._templates.values():
if params := template.matches(uri_str):
try:
return await template.create_resource(uri_str, params, context=context)
except Exception as e: # pragma: no cover
raise ValueError(f\"Error creating resource from template: {e}\")
```
It calls `template.matches(uri_str)` and then `template.create_resource(uri_str, params, context=context)`.
The `params` are likely extracted in `template.matches`.
Let's look at `src/mcp/server/fastmcp/resources/templates.py`.
In `ResourceManager.get_resource`:
```python
# Then check templates
for template in self._templates.values():
if params := template.matches(uri_str):
try:
return await template.create_resource(uri_str, params, context=context)
except Exception as e: # pragma: no cover
raise ValueError(f\"Error creating resource from template: {e}\")
```
It calls `template.matches(uri_str)` and then `template.create_resource(uri_str, params, context=context)`.
The `params` are likely extracted in `template.matches`.
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 587 tokens · stopped: STOP
Found it! In `ResourceTemplate.matches`:
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
The `match.groupdict()` returns the captured groups from the URI as-is. These are URL-encoded if they contain special characters. I need to `unquote` these values.
Wait, I should check if `unquote` is already used anywhere or if I should use `urllib.parse.unquote`.
Let's create a reproduction script to confirm this.
Found it! In `ResourceTemplate.matches`:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
The `match.groupdict()` returns the captured groups from the URI as-is. These are URL-encoded if they contain special characters. I need to `unquote` these values.
Wait, I should check if `unquote` is already used anywhere or if I should use `urllib.parse.unquote`.
Let's create a reproduction script to confirm this.
<channel|><|tool_call>call:write_file{content:<|"|>
import asyncio
from mcp.server.fastmcp.server import FastMCP
from mcp.server.fastmcp.resources.resource_manager import ResourceManager
from mcp.server.fastmcp.resources.templates import ResourceTemplate
from urllib.parse import quote
async def test_resource_decoding():
server = FastMCP("test-server")
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
return product_identifier
# Simulate a request for a resource with encoded characters
# "stick correcteur teinté anti-imperfections rechargeable au zinc"
product_name = "stick correcteur teinté anti-imperfections rechargeable au zinc"
encoded_name = quote(product_name)
uri = f"products://search/{encoded_name}"
print(f"Requesting URI: {uri}")
resource = await server._resource_manager.get_resource(uri)
if resource:
# FunctionResource stores the result of the function in a lambda
result = resource.read()
if asyncio.iscoroutine(result):
result = asyncio.run(result)
# But wait, FunctionResource.read() might be different.
# Let's look at how FunctionResource is implemented.
print(f"Result: {result}")
else:
print("Resource not found")
if __name__ == "__main__":
asyncio.run(test_resource_decoding())
<|"|>,filepath:<|"|>/tmp/repro.py<|"|>}<tool_call|><|tool_response>
Generated tokens 90 tokens · stopped: STOP
Ah, I cannot write to `/tmp`. I must write within `/workspace` and then delete it, or use `python3 - <<'PY'`. Wait, I should check `FunctionResource`'s `read` method first to make sure I'm testing it correctly.
Ah, I cannot write to `/tmp`. I must write within `/workspace` and then delete it, or use `python3 - <<'PY'`.
Wait, I should check `FunctionResource`'s `read` method first to make sure I'm testing it correctly.<channel|><|tool_call>call:read_file{filepath:<|"|>src/mcp/server/fastmcp/resources/types.py<|"|>}<tool_call|><|tool_response>
Generated tokens 311 tokens · stopped: STOP
Now I will run the reproduction using `python3 - <<'PY'`.
Now I will run the reproduction using `python3 - <<'PY'`.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import asyncio
from mcp.server.fastmcp.server import FastMCP
from urllib.parse import quote
async def test_resource_decoding():
server = FastMCP("test-server")
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
return product_identifier
product_name = "stick correcteur teinté anti-imperfections rechargeable au zinc"
encoded_name = quote(product_name)
uri = f"products://search/{encoded_name}"
print(f"Requesting URI: {uri}")
resource = await server._resource_manager.get_resource(uri)
if resource:
result = await resource.read()
print(f"Result: {result}")
if result == product_name:
print("SUCCESS: Parameters were decoded")
else:
print(f"FAILURE: Parameters were not decoded. Expected '{product_name}', got '{result}'")
else:
print("Resource not found")
if __name__ == "__main__":
asyncio.run(test_resource_decoding())
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 412 tokens · stopped: STOP
The reproduction confirmed the bug. Now I need to fix it in `src/mcp/server/fastmcp/resources/templates.py`.
I will import `unquote` from `urllib.parse` and apply it to the values in `match.groupdict()`.
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
I should change it to something like:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n params = match.groupdict()\n return {k: unquote(v) for k, v in params.items()}\n return None\n```
Wait, I need to make sure `unquote` is imported.
Let's check the imports in `src/mcp/server/fastmcp/resources/templates.py`.
The reproduction confirmed the bug. Now I need to fix it in `src/mcp/server/fastmcp/resources/templates.py`.
I will import `unquote` from `urllib.parse` and apply it to the values in `match.groupdict()`.
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
I should change it to something like:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n params = match.groupdict()\n return {k: unquote(v) for k, v in params.items()}\n return None\n```
Wait, I need to make sure `unquote` is imported.
Let's check the imports in `src/mcp/server/fastmcp/resources/templates.py`.
<channel|><|tool_call>call:read_file{end_line:20,filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:1}<tool_call|><|tool_response>
Generated tokens 93 tokens · stopped: STOP
I need to add `from urllib.parse import unquote`. Now I will apply the fix.
I need to add `from urllib.parse import unquote`.
Now I will apply the fix.
<channel|><|tool_call>call:edit_file{filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,new_string:<|"|>import re
from urllib.parse import unquote
from collections.abc import Callable<|"|>,old_string:<|"|>import re
from collections.abc import Callable<|"|>}<tool_call|><|tool_response>
Generated tokens 74 tokens · stopped: STOP
Now I will update the `matches` method. First I need to read the `matches` method's exact content.
Now I will update the `matches` method.
First I need to read the `matches` method's exact content.
<channel|><|tool_call>call:read_file{end_line:122,filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:100}<tool_call|><|tool_response>
Generated tokens 62 tokens · stopped: STOP
I read the wrong part of the file. I need the `matches` method.
I read the wrong part of the file. I need the `matches` method.<channel|><|tool_call>call:read_file{end_line:80,filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:50}<tool_call|><|tool_response>
Generated tokens 60 tokens · stopped: STOP
Still not there. Let me read from line 81.
Still not there. Let me read from line 81.
<channel|><|tool_call>call:read_file{end_line:110,filepath:<|"|>src/mcp/server/fastmcp/resources/templates.py<|"|>,start_line:81}<tool_call|><|tool_response>
Generated tokens 526 tokens · stopped: STOP
Now I have the `matches` method.
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
I will change it to:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n```
Now I have the `matches` method.
```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}$\", uri)\n if match:\n return match.groupdict()\n return None\n```
I will change it to:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Check if URI matches template and extract parameters.\"\"\"\n # Convert template to regex pattern\n pattern = self.uri_template.replace(\"{\", \"(?P<\").replace(\"}\", \">[^/]+)\")\n match = re.match(f\"^{pattern}$\", uri)\n if match:\n return {k: unquote(v) for k, v in match.groupdict().items()}\n return None\n```
<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."""
# 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 308 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'
import asyncio
from mcp.server.fastmcp.server import FastMCP
from urllib.parse import quote
async def test_resource_decoding():
server = FastMCP("test-server")
@server.resource("products://search/{product_identifier}")
def find_similar_products(product_identifier: str):
return product_identifier
product_name = "stick correcteur teinté anti-imperfections rechargeable au zinc"
encoded_name = quote(product_name)
uri = f"products://search/{encoded_name}"
print(f"Requesting URI: {uri}")
resource = await server._resource_manager.get_resource(uri)
if resource:
result = await resource.read()
print(f"Result: {result}")
if result == product_name:
print("SUCCESS: Parameters were decoded")
else:
print(f"FAILURE: Parameters were not decoded. Expected '{product_name}', got '{result}'")
else:
print("Resource not found")
if __name__ == "__main__":
asyncio.run(test_resource_decoding())
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 77 tokens · stopped: STOP
The reproduction script now passes. I should also check if there are any existing tests that I should run to make sure I didn't break anything. I'll search for tests related to resources.
The reproduction script now passes.
I should also check if there are any existing tests that I should run to make sure I didn't break anything. I'll search for tests related to resources.
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn "Resource" tests/ | grep "test_" | head -n 20<|"|>}<tool_call|><|tool_response>
Generated tokens 52 tokens · stopped: STOP
These don't seem to be FastMCP specific tests. Let me look for `fastmcp` in `tests/`.
These don't seem to be FastMCP specific tests. Let me look for `fastmcp` in `tests/`.
<channel|><|tool_call>call:run_command{command:<|"|>find tests/ -name "*fastmcp*"<|"|>}<tool_call|><|tool_response>
Generated tokens 48 tokens · stopped: STOP
Okay, let's see what's in `tests/server/fastmcp`.
Okay, let's see what's in `tests/server/fastmcp`.
<channel|><|tool_call>call:run_command{command:<|"|>find tests/server/fastmcp -name "*.py"<|"|>}<tool_call|><|tool_response>
Generated tokens 69 tokens · stopped: STOP
`tests/server/fastmcp/resources/test_resource_template.py` seems exactly what I need.
`tests/server/fastmcp/resources/test_resource_template.py` seems exactly what I need.
<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 47 tokens · stopped: STOP
All tests passed. I'll double check `git status --short` and `git diff` before submitting.
All tests passed.
I'll double check `git status --short` and `git diff` before submitting.
<channel|><|tool_call>call:run_command{command:<|"|>git status --short && git diff<|"|>}<tool_call|><|tool_response>
Generated tokens 207 tokens · stopped: STOP
The diff looks correct. I've added the `unquote` import and used it in `matches` to decode the extracted parameters.
I'll do one final check of the `ResourceTemplate.matches` method to make sure no other place needs this.
The current implementation of `matches` is:
```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}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
This looks correct.
I am ready to submit.
The diff looks correct. I've added the `unquote` import and used it in `matches` to decode the extracted parameters.
I'll do one final check of the `ResourceTemplate.matches` method to make sure no other place needs this.
The current implementation of `matches` is:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
"""Check if URI matches template and extract parameters."""
# Convert template to regex pattern
pattern = self.uri_template.replace("{", "(?P<").replace("}", ">[^/]+)")
match = re.match(f"^{pattern}$", uri)
if match:
return {k: unquote(v) for k, v in match.groupdict().items()}
return None
```
This looks correct.
I am ready to submit.
<channel|><|tool_call>call:submit_patch{}<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/issues/test_973_url_decoding.py::test_template_matches_decodes_space tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_exception_has_method_attribute tests/server/test_stateless_mode.py::test_elicit_url_fails_in_stateless_mode tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode [gw9] [ 8%] PASSED tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable [gw10] [ 16%] PASSED tests/server/test_stateless_mode.py::test_exception_has_method_attribute [gw4] [ 25%] PASSED tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode [gw7] [ 33%] PASSED tests/server/test_stateless_mode.py::test_elicit_url_fails_in_stateless_mode tests/issues/test_973_url_decoding.py::test_template_matches_preserves_plus_sign [gw3] [ 41%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_preserves_plus_sign [gw2] [ 50%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase [gw11] [ 58%] PASSED tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error [gw5] [ 66%] PASSED tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode [gw6] [ 75%] PASSED tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode [gw1] [ 83%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters [gw8] [ 91%] PASSED tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode [gw0] [100%] PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_space ═══════════════════════════════ 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-2113e3e5a90448f096925a0b2042654c.xml -- =========================== short test summary info ============================ PASSED tests/server/test_stateless_mode.py::test_stateless_error_message_is_actionable PASSED tests/server/test_stateless_mode.py::test_exception_has_method_attribute PASSED tests/server/test_stateless_mode.py::test_list_roots_fails_in_stateless_mode 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_preserves_plus_sign PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_complex_phrase PASSED tests/server/test_stateless_mode.py::test_stateful_mode_does_not_raise_stateless_error PASSED tests/server/test_stateless_mode.py::test_create_message_fails_in_stateless_mode PASSED tests/server/test_stateless_mode.py::test_elicit_form_fails_in_stateless_mode PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_accented_characters PASSED tests/server/test_stateless_mode.py::test_elicit_deprecated_fails_in_stateless_mode PASSED tests/issues/test_973_url_decoding.py::test_template_matches_decodes_space ============================= 12 passed in 24.79s ==============================
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="24.790" timestamp="2026-11-14T03:39:38.199882+00:00" hostname="dd8129d8d71e"><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_complex_phrase" time="0.003" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_accented_characters" time="0.083" /><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_list_roots_fails_in_stateless_mode" time="0.002" /><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_exception_has_method_attribute" time="0.002" /><testcase classname="tests.server.test_stateless_mode" name="test_create_message_fails_in_stateless_mode" 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_elicit_url_fails_in_stateless_mode" time="0.003" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_preserves_plus_sign" time="0.003" /><testcase classname="tests.server.test_stateless_mode" name="test_elicit_deprecated_fails_in_stateless_mode" time="0.003" /><testcase classname="tests.issues.test_973_url_decoding" name="test_template_matches_decodes_space" time="0.003" /></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.
[ 14.4s] 💭 (627 chars) "The objective is to fix a bug where dynamic URL resource parameters in the MCP Python SDK
are not being URL-decoded befo..."
[ 14.4s] 🔧 run_command grep -rn --include="*.py" -e "resource" src/mcp | grep -E "server|types" | head
[ 14.5s] → src/mcp/shared/auth_utils.py:9:def resource_url_from_server_url(url: str | HttpUrl | AnyUrl) -> str:
[ 23.5s] 💭 (252 chars) "The `grep` results above show `src/mcp/types.py` and `src/mcp/shared/auth_utils.py`. But the
example uses a decorator `@..."
[ 23.5s] 🔧 run_command grep -rn --include="*.py" "resource" src/mcp/server
[ 23.6s] → src/mcp/server/fastmcp/resources/templates.py:12:from mcp.server.fastmcp.resources.types import
FunctionResource, Resour
[ 32.3s] 💭 (184 chars) "Wait, if the user uses `@mcp.resource("products://search/{product_identifier}")`, it looks
like `FastMCP` is being used...."
[ 32.3s] 🔧 run_command find src/mcp/server/fastmcp -name "*.py"
[ 32.4s] → src/mcp/server/fastmcp/utilities/types.py
[ 35.8s] 💭 (96 chars) "Okay, `src/mcp/server/fastmcp/server.py` probably has the `@resource` decorator. Let's check
it."
[ 35.8s] 📖 read_file (src/mcp/server/fastmcp/server.py)
[ 35.9s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/server.py', 'content': '"""FastMCP - A more
ergonomic interface for…
[ 42.0s] 💭 (106 chars) "I need to find the `resource` method in `FastMCP`. Let me read more of
`src/mcp/server/fastmcp/server.py`."
[ 42.0s] 🔧 run_command grep -n "def resource" src/mcp/server/fastmcp/server.py
[ 42.1s] → 519: def resource(
[ 46.2s] 💭 (30 chars) "Now I'll read around line 519."
[ 46.2s] 📖 read_file (src/mcp/server/fastmcp/server.py)
[ 46.3s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/server.py', 'content': '\n def
add_resource(self, resource: Reso…
[ 51.2s] 💭 (160 chars) "The `resource` decorator calls `self._resource_manager.add_template`. Let's look at
`ResourceManager` in `src/mcp/server..."
[ 51.2s] 📖 read_file (src/mcp/server/fastmcp/resources/resource_manager.py)
[ 51.2s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/resource_manager.py', 'content':
'"""Resource manager fun…
[ 63.3s] 💭 (668 chars) "In `ResourceManager.get_resource`:
```python
# Then check templates
for template in self._templates.valu..."
[ 63.3s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 63.3s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '"""Resource
template functiona…
[ 102.0s] 💭 (771 chars) "Found it! In `ResourceTemplate.matches`:
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"..."
[ 102.0s] 📝 write_file (/tmp/repro.py, 36 lines)
[ 102.1s] ❌ {'status': 'error', 'error_type': 'FileWriteError', 'error_message': "Path traversal detected:
'/tmp/repro.py' escapes w…
[ 109.2s] 💭 (211 chars) "Ah, I cannot write to `/tmp`. I must write within `/workspace` and then delete it, or use
`python3 - <<'PY'`.
Wait, I s..."
[ 109.2s] 📖 read_file (src/mcp/server/fastmcp/resources/types.py)
[ 109.3s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/types.py', 'content': '"""Concrete
resource implementatio…
[ 123.0s] 💭 (57 chars) "Now I will run the reproduction using `python3 - <<'PY'`."
[ 123.0s] 🔧 run_command (32 lines) python3 - <<'PY'
[ 124.0s] → Requesting URI:
products://search/stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc
[ 140.4s] 💭 (1254 chars) "The reproduction confirmed the bug. Now I need to fix it in
`src/mcp/server/fastmcp/resources/templates.py`.
I will imp..."
[ 140.4s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 140.5s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '"""Resource
template functiona…
[ 193.6s] 💭 (76 chars) "I need to add `from urllib.parse import unquote`.
Now I will apply the fix."
[ 193.6s] ✏️ edit_file (src/mcp/server/fastmcp/resources/templates.py)
[ 193.7s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'occurrences': 1,
'strategy': 'exact', 'di…
[ 197.4s] 💭 (99 chars) "Now I will update the `matches` method.
First I need to read the `matches` method's exact content."
[ 197.4s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 197.5s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': ' ) ->
Resource:\n ""…
[ 202.5s] 💭 (63 chars) "I read the wrong part of the file. I need the `matches` method."
[ 202.5s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 202.6s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': ' meta:
dict[str, Any] |…
[ 208.1s] 💭 (42 chars) "Still not there. Let me read from line 81."
[ 208.1s] 📖 read_file (src/mcp/server/fastmcp/resources/templates.py)
[ 208.1s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'content': '
fn=fn,\n …
[ 227.9s] 💭 (910 chars) "Now I have the `matches` method.
```python
def matches(self, uri: str) -> dict[str, Any] | None:
\"\"\"Chec..."
[ 227.9s] ✏️ edit_file (src/mcp/server/fastmcp/resources/templates.py)
[ 228.0s] ✓ {'status': 'ok', 'filepath': 'src/mcp/server/fastmcp/resources/templates.py', 'occurrences': 1,
'strategy': 'exact', 'di…
[ 235.6s] 💭 (63 chars) "Now I will run the reproduction script again to verify the fix."
[ 235.6s] 🔧 run_command (32 lines) python3 - <<'PY'
[ 236.0s] → Requesting URI:
products://search/stick%20correcteur%20teint%C3%A9%20anti-imperfections%20rechargeable%20au%20zinc
[ 244.6s] 💭 (188 chars) "The reproduction script now passes.
I should also check if there are any existing tests that I should run to make sure ..."
[ 244.6s] 🔧 run_command grep -rn "Resource" tests/ | grep "test_" | head -n 20
[ 244.7s] → tests/test_examples.py:14:from mcp.types import TextContent, TextResourceContents
[ 247.9s] 💭 (85 chars) "These don't seem to be FastMCP specific tests. Let me look for `fastmcp` in `tests/`."
[ 247.9s] 🔧 run_command find tests/ -name "*fastmcp*"
[ 247.9s] → tests/server/fastmcp
[ 250.9s] 💭 (49 chars) "Okay, let's see what's in `tests/server/fastmcp`."
[ 250.9s] 🔧 run_command find tests/server/fastmcp -name "*.py"
[ 250.9s] → tests/server/fastmcp/test_integration.py
[ 253.9s] 💭 (85 chars) "`tests/server/fastmcp/resources/test_resource_template.py` seems exactly what I need."
[ 253.9s] 🔧 run_command pytest tests/server/fastmcp/resources/test_resource_template.py -q --tb=short --
[ 279.2s] → bringing up nodes...
[ 285.1s] 💭 (91 chars) "All tests passed.
I'll double check `git status --short` and `git diff` before submitting."
[ 285.1s] 🔧 run_command git status --short && git diff
[ 285.1s] → M src/mcp/server/fastmcp/resources/templates.py
[ 298.0s] 💭 (732 chars) "The diff looks correct. I've added the `unquote` import and used it in `matches` to decode
the extracted parameters.
I'..."
[ 298.0s] 🤖 submit_patch
[ 298.1s] → submit_patch: {"status": "ok", "patch_size": 802, "files_changed": 1}
[ 313.6s] 💭 (286 chars) "I have fixed the bug where dynamic URL resource parameters in `FastMCP` were not being
URL-decoded. I added `urllib.pars..."
[ 313.6s] ✅ Agent finished: The bug was caused by `ResourceTemplate.matches` extracting URI parameters using
`match.groupdict()` without URL-decoding them. I imported `unquote` from `urllib.parse` and updated the `matches`
metho...
Native result row
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"resolved": true,
"status_counts": {
"PASSED": 12
},
"strict_clean_patch": true,
"test_exit_code": 0
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"instance_id": "modelcontextprotocol__python-sdk-1864",
"pass_idx": 0,
"patch_chars": 802,
"phase1_seconds": 323.16,
"repo": "modelcontextprotocol/python-sdk",
"request_log_path": "/kaggle-root/working/r31/rollouts_X/requests/modelcontextprotocol__python-sdk-1864__p0__r2.jsonl",
"resolved": true,
"rollout_idx": 2,
"run_key": "modelcontextprotocol__python-sdk-1864__p0__r2",
"strict_clean_patch": true,
"tool_calls": 23,
"total_llm_calls": 25,
"trace_path": "/kaggle-root/working/r31/rollouts_X/traces/trace_modelcontextprotocol__python-sdk-1864__p0__r2.json"
}