find_context_parameter treats a Context return annotation as a parameter

Initial checks

• I tested the current main branch (6e30452).
• I searched existing issues and pull requests for this behavior.

Description

find_context_parameter() iterates over every entry returned by typing.get_type_hints(). That mapping includes the function return annotation under the special key "return", even though it is not a parameter.

As a result, a tool, prompt, or resource function whose return annotation is Context (or a union containing Context) is incorrectly recorded as having a context parameter named "return". The SDK later attempts to inject context as a keyword argument with that name, which can produce an unexpected-keyword error when the callable is invoked.

Expected: context detection only examines actual function parameters and ignores the return annotation.

Example code

from mcp.server.mcpserver import Context
from mcp.server.mcpserver.utilities.context_injection import find_context_parameter

def fn(value: int) -> Context:
    ...

print(find_context_parameter(fn))  # current: "return"; expected: None

Environment

• Python 3.12
• MCP Python SDK main at 6e30452

I used AI assistance while investigating this issue and reviewed and reproduced the behavior locally.

Inizia in mcp/server/mcpserver/utilities/context_injection.py, in find_context_parameter(), e riproduci l’esempio con un’annotazione di ritorno Context. Conferma che il rilevamento esamini solo i parametri effettivi, ignori l’annotazione "return" e non segnali più "return" come parametro di contesto.