dict[str, T] tool return types lose Annotated/Field metadata in output schema

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

Tools that return a string-keyed dict (dict[str, T]) lose any Annotated/Field metadata on the return type when the output schema is generated. A Field(description=...) on the return annotation shows up in the output schema for every other return type, but for dict[str, T] it's dropped.

I'd expect the description to be preserved, the same as other return types. Looks like the dict[str, T] branch in _try_create_model_and_schema builds the model from the Annotated-stripped type instead of the original annotation (there's an existing TODO on that line).

Have a simple, tested fix ready to go. Love the project and would love to contribute if possible!

Example Code

from typing import Annotated
from pydantic import Field
from mcp.server.mcpserver.utilities.func_metadata import func_metadata

def get_config() -> Annotated[dict[str, int], Field(description="Configuration values")]:
    return {"timeout": 30}

print(func_metadata(get_config).output_schema)
# {'type': 'object', 'additionalProperties': {'type': 'integer'}, 'title': 'get_configDictOutput'}
# expected to also include: 'description': 'Configuration values'

Python & MCP Python SDK

Python 3.14.5
mcp: main branch (mcpserver / V2)

Commencez dans mcp.server.mcpserver.utilities.func_metadata, au niveau de _try_create_model_and_schema, en vous concentrant sur la branche dict[str, T] et son TODO existant. Examinez l’exemple get_config fourni et les tests environnants de génération de schéma, puis vérifiez qu’une description Annotated Field apparaît dans le schéma de sortie pour les valeurs de retour de dictionnaires dont les clés sont des chaînes de caractères.