Return METHOD_NOT_FOUND for invalid request methods#2372

Open

raashish1601 wants to merge 1 commit intomodelcontextprotocol:mainfrom

raashish1601:contributor-26/python-sdk-1561

raashish1601 commented Mar 28, 2026

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


          Return method-not-found for unknown request methods

274581e

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels

None yet