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fix(mcp): expose every API route as an MCP tool, and serve streamable HTTP - #160
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Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe shared MCP module now supports SSE and Streamable HTTP. Both API services mount MCP after registering routes. Documentation and tests cover the transports, endpoints, and exposed tools. ChangesMCP transport support
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant MCPClient
participant APIService
participant SessionManager
MCPClient->>APIService: POST /mcp/http initialize
APIService->>SessionManager: Forward request
SessionManager-->>APIService: Return session response
APIService-->>MCPClient: Return session response
MCPClient->>APIService: Request tools/list with session ID
APIService->>SessionManager: Forward request
SessionManager-->>APIService: Return tool names
APIService-->>MCPClient: Return tool names
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Review comments at @services/configiq-py/configiq/mcp.py:
- Line 51: Update the HTTP adapter used by server.mount_http so Streamable HTTP
GET responses forward ASGI headers and events as they arrive; if that is not
supported, disable GET support rather than advertising a route that cannot
deliver its SSE stream.
- Line 51: Configure a finite SDK session_idle_timeout for the stateful HTTP
adapter used by server.mount_http so abandoned MCP sessions expire and release
their transports and tasks; retain the stateful transport behavior for active
sessions.
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services/aicostings/README.mdservices/aicostings/tests/unit/test_mcp.pyservices/aicostings/tools/api_service/app.pyservices/aisimulators/tests/unit/tools/test_api_service.pyservices/aisimulators/tools/api_service/README.mdservices/aisimulators/tools/api_service/app.pyservices/configiq-py/README.mdservices/configiq-py/configiq/mcp.py
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@flg77 thanks! Looks good. I'm working through the CodeRabbit review commentary now. Your original commit lacks a signed-off-by line though so we'll fail CI - can you add one? or with your ack I can add it for you. |
… HTTP Both services called configiq.mcp.mount() before declaring their routes. fastapi-mcp builds its tool list from the routes that exist when the server is constructed, so aisimulators exposed only get_backends (not /recommend, /predict, /memory, /models or /systems, which its README promises), and aicostings exposed no tools at all. - aisimulators, aicostings: mount after the last route; keep the server as _MCP_SERVER so tests can check what clients see. - configiq.mcp.mount(): keep SSE at /mcp (unchanged for existing clients) and also serve MCP streamable HTTP at /mcp/http from the same server — the transport the MCP spec recommends since 2025-03-26, needed by clients that do not speak SSE. - Tests: assert the full tool list and both transports; aisimulators also lists the tools over /mcp/http. They fail on the current main. - READMEs: document both endpoints and the mount-after-routes rule. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Nathan Scott <nathans@redhat.com>
Use the native MCP SDK ASGI transport so Streamable HTTP GET responses stream correctly without forking fastapi-mcp. Configure 30-minute session expiry, preserve existing FastAPI lifespan state, and cleanly manage transport startup and shutdown. Constrain the MCP SDK to >=1.29,<2.0, update both service lockfiles, and add lifecycle and streaming regression coverage. Signed-off-by: Nathan Scott <nathans@redhat.com>
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@flg77 I deployed these changes and tested further. One issues I found relates to the way we have our deployments setup - i.e. with multiple, independent aisimulators backend pods. This is proving problematic in terms of MCP session stickiness. So, everything works, code-wise, but in practice a request will frequently be routed to a new pod part way through a session and errors result. I've been working on fixing this today - and forming a single unified ConfigIQ MCP server for both aisimulators and aicostings (and any future APIs we create) - via PR #166 Its working well now so I'll cutover to this as the final solution shortly, solving the stickiness problem in the process. |
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Problem
configiq.mcp.mount()is called near the top of both services'app.py, before their routes are declared. fastapi-mcp builds its tool list from the routes that exist whenFastApiMCP(app, ...)runs, and routes added later are never picked up. As a result:mount()aisimulators/backendsget_backends_backends_getonly./recommend,/predict,/memory,/modelsand/systemsare missing, although the README lists them.aicostingsThe existing test (
test_mcp_tools_wrap_api_endpoints) only checks that the helper module was imported, so this went unnoticed.A second, smaller gap: the endpoint is SSE-only (
mount_sse("/mcp")). Clients that only speak MCP streamable HTTP cannot connect. The MCP spec has recommended streamable HTTP since 2025-03-26, and several agent runtimes no longer implement SSE.Change
aisimulators,aicostings: theif _MCP: mcp_support.mount(...)block moves below the last route, just above the entrypoint. A comment explains why it must stay there. The returned server is kept as_MCP_SERVERso tests can check what clients will see.configiq.mcp.mount(): keeps SSE at/mcp, which is unchanged for existing clients (Claude Desktop config and MCP Inspector, as in the READMEs). It also serves the same tools over streamable HTTP at/mcp/httpfrom the sameFastApiMCPinstance. The routes do not collide: SSE usesGET /mcpandPOST /mcp/messages/, while HTTP usesGET|POST|DELETE /mcp/http. The docstring and README now say to callmount()after the last route.aisimulators: the weak test is replaced by three tests. One asserts every expected tool is present, one asserts both transports are routed, and one does a real streamable-HTTPinitialize → tools/listround trip throughTestClient.aicostings: a newtests/unit/test_mcp.pychecks the tool list and the routes. It needs no Valkey.mainand pass with this change.aisimulatorstool list now includes/backends.No API, schema or dependency changes. The
mcpextra already pulls infastapi-mcp, which providesmount_http.Testing
Run as
ci.ymldoes:uv sync --extra otel --extra mcp, thenruff check .andpytest, per service.main)aisimulatorsruffaisimulatorspytestaicostingsruffaicostingspytest(local Redis standing in for Valkey)Run on this branch rebased onto
mainat6a4ddba.End-to-end check against the real patched
aisimulatorsrunning under uvicorn:/mcp/httplistsget_backends,get_models,get_systems,post_memory,post_predictandpost_recommend.get_systemsreturns the system catalogue.main, the same client gets one tool, or fails atinitializewhen it does not speak SSE.Context
Found while wiring AISimulators into an agent platform (ACC) as an MCP server for latency-aware GPU sizing. The client there speaks streamable HTTP only, and needs
/recommendand/predictas tools.Both services called configiq.mcp.mount() before declaring their routes. fastapi-mcp builds its tool list from the routes that exist when the server is constructed, so aisimulators exposed only get_backends (not /recommend, /predict, /memory, /models or /systems, which its README promises), and aicostings exposed no tools at all.
Summary by CodeRabbit
/mcp/http, alongside SSE at/mcp.GET,POST, andDELETErequests; SSE usesGET.