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GeezerVison is showing github.com — Return METHOD_NOT_FOUND for invalid request methods by raashish1601 · Pull Request #2372 · modelcontextprotocol/python-sdk

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@raashish1601

@raashish1601 raashish1601 commented Mar 28, 2026

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Fixes #1561.

Summary

  • return METHOD_NOT_FOUND for unknown JSON-RPC request methods instead of collapsing them into the generic request-validation INVALID_PARAMS fallback
  • keep INVALID_PARAMS for malformed known methods by only special-casing method names that are outside the typed client request union
  • add a focused regression proving invalid/method returns -32601 while malformed initialize still returns -32602

Testing

  • PYTHONPATH=src python -m pytest -o addopts="" tests/issues/test_1561_invalid_method_names.py -q
  • python -m ruff check src/mcp/shared/session.py src/mcp/server/session.py tests/issues/test_1561_invalid_method_names.py
  • git diff --check

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@raashish1601
Return method-not-found for unknown request methods
274581e
@borisowvalia borisowvalia mentioned this pull request Jul 29, 2026
Unknown methods return -32602 Invalid params instead of -32601 Method not found #3193
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@maxisbey

maxisbey commented Jul 29, 2026

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Thanks for the PR. This has since landed via #2836. Closing as part of a general backlog cleanup following the v2 release. If this is still relevant against v2, feel free to reopen.

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@maxisbey maxisbey closed this Jul 29, 2026
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Invalid method names return error code -32602 instead of -32601

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@raashish1601 @maxisbey
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