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fix(mcp): support fastmcp 3 and 4, parse adapter requests - #291
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The adapter converted each fastmcp tool to the MCP protocol Tool and read inputSchema/outputSchema. MCP SDK 2, pulled in by fastmcp 4, renamed those fields to snake_case, so mypy fails and every listing warns. fastmcp's own Tool exposes parameters and output_schema unchanged across both majors, so read them directly and widen the extra to fastmcp>=3,<5. The adapter subscriptions never passed data_type, so handlers received raw dicts and crashed on the first attribute access. Declare the request models on both subscriptions and add an end-to-end test over the in-memory transport covering tool listing, a successful call and an error call. Supersedes #288.
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On the QualOps high and medium findings ( Both attributes are declared fields on fastmcp's own Evidence:
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Supersedes #288.
Why
fastmcp 4 depends on MCP SDK 2, which renamed the protocol Tool fields
inputSchema/outputSchemato snake_case. The adapter read the camelCase names, so with extras installed in CI (#290) the lint job fails on #288 with two mypy errors, and every tool listing emits aFastMCPDeprecationWarning. On MCP SDK 1 the snake_case names do not exist, so no single read satisfies the>=3,<5range Dependabot proposed.What
name,description,parametersandoutput_schemafrom fastmcp's ownTool, which is identical on 3.x and 4.x. The conversion to the protocol Tool is gone.mcpextra constraint isfastmcp>=3,<5; lock resolves to fastmcp 4.0.5. Not a breaking change: projects pinned to fastmcp 3 keep resolving.data_type, so handlers received raw dicts and crashed onmessage.data. This predates the fastmcp bump. Both subscriptions now declare their request model.tests/test_mcp.pyruns the adapter over the in-memory transport and covers tool listing, a successful call and an error call. It fails on the unmodified adapter with'dict' object has no attribute 'data'.Verification
tests/test_mcp.pywith-W erroron fastmcp 4.0.5, 4.0.3 and 3.4.7 (Python 3.10): passed.