fix(community-v3): inject tool context without deep-copying the tool#38
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When enriching a tool's input schema with the AgentCat `context` parameter, the FastMCP v3 middleware deep-copied the entire tool object on every `tools/list` request. FastMCP v3 tools generated from an OpenAPI specification hold a reference to their `httpx.AsyncClient`, which contains a `threading.RLock`. Deep-copying that object raised `TypeError: cannot pickle '_thread.RLock' object`, and the resulting fallback returned the tool unmodified. As a consequence, context injection was silently skipped for every affected tool and the failure was logged on each request, producing a high volume of diagnostic errors. Only the `parameters` schema (a plain dictionary) is modified during injection, so this change copies just that schema and reuses the rest of the tool by reference via `Tool.model_copy`. This avoids traversing non-copyable fields entirely, restores context injection for OpenAPI-generated tools, and leaves the server's original tool objects unmutated. The remaining copy-failure log line now records the resolved FastMCP version to aid future diagnosis. Adds regression coverage that reproduces the RLock failure with an OpenAPI-generated tool and verifies injection, non-mutation, and the version-tagged log message. Verified against FastMCP 3.0.0b1 and 3.4.4.
…absent The regression tests exercise the FastMCP v3 OpenAPI middleware path and require FastMCP v3+. Guard the module so it is skipped rather than failing collection in the no-FastMCP CI job and on the FastMCP v2 compatibility matrix: defer the fastmcp/httpx imports behind a try/except and gate the module with a skipif on the resolved FastMCP major version.
kashishhora
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Jul 9, 2026
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naji247
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The community test suite previously exercised only plain function tools, which deep-copy cleanly. That gap let the context-injection regression fixed in #38 ship green: FastMCP v3 tools that hold live runtime state (an httpx client on OpenAPI-generated tools, a client factory on proxy tools, a sub-server reference on mounted tools) failed to deep-copy and silently lost context injection. Add end-to-end coverage that drives the real middleware dispatch against those tool types, entirely in-process via httpx.MockTransport (no network): - tests/test_utils/community_openapi_server.py: factories for OpenAPI, proxy, and mounted FastMCP v3 servers, plus a multi-endpoint OpenAPI spec. - tests/community/test_community_v3_openapi.py: tools/list injects context on every tool, no copy failure is logged, cached tools are not mutated, tools/call strips context and captures it as intent without leaking it downstream, HTTP errors are captured, the tools/list event serializes OpenAPI tools, and get_more_tools coexists with generated tools. - tests/community/test_community_v3_runtime_state_tools.py: parametrized guard over openapi/proxy/mounted asserting context injection with no copy failures. All modules are FastMCP v3-only and skip cleanly when FastMCP is absent or on the v2 compatibility matrix. Verified on FastMCP 3.0.0b1 and 3.4.4.
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Summary
_inject_context_into_toolsdeep-copied the entire tool object on everytools/listrequest in order to add the AgentCatcontextparameter to its input schema. FastMCP v3 tools generated from an OpenAPI specification hold a reference to theirhttpx.AsyncClient, which contains athreading.RLock. Deep-copying that object raisesTypeError: cannot pickle '_thread.RLock' object. The failure was caught and the tool returned unmodified, so context injection was silently skipped for every affected tool while the error was logged on each request — generating a high volume of SDK diagnostic errors.parametersschema (a plain dictionary) is mutated during injection, so we now copy just that schema and reuse the rest of the tool by reference viaTool.model_copy. This avoids traversing non-copyable fields, restores context injection for OpenAPI-generated tools, and leaves the server's original tool objects unmutated.1.0.0->1.0.1.Impact
Customers running OpenAPI-generated FastMCP v3 servers on
agentcat==1.0.0were not receiving tool-call context/intent capture, and their processes emitted a copy-failure log per tool on everytools/list. This restores the intended behavior and removes the error volume.Test plan
uv run pytest tests/community/test_community_v3_inject_context.py -v- new regression tests pass:contextis injected into the tool's parameters and marked requireduv run pytest tests/community/ tests/test_context_parameters.py -q- full community suite passes (no regressions)