fix(fastmcp): support PEP 604 union return types#2599

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MukundaKatta wants to merge 1 commit into

modelcontextprotocol:mainfrom

MukundaKatta:codex/py310-union-tool-return

MukundaKatta commented May 15, 2026

Summary

define wrapped structured-output fields using Pydantic's explicit required field tuple
add regression coverage for FastMCP tools returning container/primitive PEP 604 unions like dict | list | str

Fixes #2591

Test plan

uv run pytest tests/server/mcpserver/test_func_metadata.py -k "structured_output"
uv run pytest tests/server/mcpserver/test_func_metadata.py


          fix fastmcp pep 604 union output schema

794181b

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