It is not possible to define a Resource that takes only the Context parameter as an argument.

Initial Checks

• I confirm that I'm using the latest version of MCP Python SDK
• I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue

Description

Problem

Currently, it is not possible to define a Resource that takes only the Context parameter as an argument. When attempting to create such a resource, the registration logic incorrectly classifies it as a template resource instead of a regular resource.

Expected Behavior

Resources with only a Context parameter should be registered as regular resources, not template resources.

Current Behavior

Resources with only a Context parameter are incorrectly registered as template resources, causing them to not appear in the resource list and fail when accessed.

Root Cause

The parameter validation logic in the FastMCP.resource() decorator doesn't properly distinguish between effective function parameters and Context parameters. It treats any function with parameters as a potential template resource, even when the only parameter is a Context.

Solution

1. Fix the parameter validation logic to exclude Context parameters when determining if a resource should be a template
2. Update the Resource.read() method signature to accept an optional context parameter
3. Update all resource implementations to support the new signature

This change maintains full backward compatibility while enabling context-only resources.

Example Code

@mcp.resource("resource://user_profile")
def get_user_profile(ctx: Context) -> str:
    # Something Code ...

Python & MCP Python SDK

Python 3.13.5
MCP Python SDK v1.15.0

Start with the FastMCP.resource() decorator's parameter validation and inspect how Context-only functions are classified. Then trace Resource.read() and the existing resource implementations to update the call signature consistently; done means Context-only resources appear in the resource list and can be accessed without breaking existing resources.