fix: correct MCPServer.call_tool return type and remove dead code#2700
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Ar-maan05 wants to merge 5 commits into
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fix: correct MCPServer.call_tool return type and remove dead code#2700Ar-maan05 wants to merge 5 commits into
Ar-maan05 wants to merge 5 commits into
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added 4 commits
May 28, 2026 12:36
Define the call_tool return union once as the ToolResult type alias and reference it from _handle_call_tool, call_tool, and the migration guide so the signature can't drift across locations. Add a regression test that drives a tool with an output schema through _handle_call_tool and asserts the resulting CallToolResult has both content and structured_content populated, pinning the reachable tuple path.
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I checked this against #2695 while looking for non-duplicative work. The shape cleanup looks consistent with Local validation on this PR head: uv run --frozen pytest tests/server/mcpserver/test_server.py -qResult: So from a regression-coverage angle this looks well pinned down to me. |
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Description
This PR addresses the dead-code path and incorrect return type annotation on MCPServer.call_tool() described in #2695.
src/mcp/server/mcpserver/server.py, theisinstance(result, dict)check inside_handle_call_tool()is unreachable. As traced in the issue,self.call_tool()invokes the tool manager withconvert_result=True, which delegates toFuncMetadata.convert_result. This converter function never returns a raw dict (returningCallToolResult,Sequence[ContentBlock], ortuple[Sequence[ContentBlock], dict[str, Any]]instead).import jsonfromsrc/mcp/server/mcpserver/server.py.MCPServer.call_tool()'s return type signature to accurately reflect the actual runtime types:CallToolResult | Sequence[ContentBlock] | tuple[Sequence[ContentBlock], dict[str, Any]]docs/migration.mdto assist developers migrating to v2.Related Issues
Closes #2695
Verification
• Verified that the test suite passes successfully (1,194 passed).
• Verified type checking passes cleanly with
pyright(0 errors, 0 warnings).• Ran
coverageandstrict-no-coverto verify that code coverage remains at100.00%and no unused coverage pragmas exist.