Microsoft Copilot | Microsoft 365 Copilot | Development
Building and customizing solutions using Microsoft 365 Copilot APIs and tools
Custom Microsoft 365 Copilot federated MCP connector is visible/connectable in some Copilot experiences, but Microsoft 365 Copilot Chat and Excel do not consistently invoke the MCP server. Requests fail before reaching the MCP endpoint
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Thomas Nicolette
5
Reputation points
The MCP server is a Python FastMCP application running behind FastAPI/Uvicorn. The MCP endpoint is reachable and responds successfully when Microsoft performs connector/tool discovery.
This is a federated MCP connector, not a synced/indexed Work IQ connector. Microsoft documentation describes federated connectors as using MCP to retrieve data in real time without indexing the external data into Microsoft 365, and lists Microsoft 365 Copilot Chat, Copilot in Excel, and Researcher agent as supported experiences.
Microsoft Copilot | Microsoft 365 Copilot | Development
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Prasad-MSFT 10,546 Reputation points Microsoft External Staff Moderator2026-07-03T05:43:37.0233333+00:00 Federated MCP connectors are supported in Microsoft 365 Copilot Chat, Copilot in Excel, and Researcher, but invocation is still controlled by Copilot’s orchestration layer, so tool discovery success does not guarantee the MCP server will be called for every prompt. Since requests fail before reaching the MCP endpoint, this is likely an orchestration/routing, eligibility, authentication, or experience-specific support issue rather than a FastMCP/FastAPI server issue.
Ensure the connector is admin-enabled, user-connected, available for the target users, and that the MCP tool schema clearly exposes supported
search/fetchstyle capabilities with valid auth. Also validate that the prompt strongly matches the connector/tool description, as Copilot may skip the MCP tool if it decides the tool is not relevant. -
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Max 0 Reputation points2026-09-14T06:15:46.0333333+00:00 We're in the same boat - using @modelcontextprotocol/sdk (latest published, v1.30.0) behind a Next.js API route. Connector discovers and lists tools correctly - tools/list returns a clean, well-formed response with our tools' names, descriptions, and schemas. But tools/call is never sent. We've reproduced this identically across:
- A fresh conversation vs. continuing the same thread
- Explicitly naming the tool in the prompt (e.g. "call the X tool") vs. a natural-language ask
- Both SSE-framed and plain-JSON response bodies for our MCP responses
- A 24-hour wait in case of any activation/propagation delay - no change
Every attempt: initialize - tools/list all succeed, then nothing. Copilot's own explanation to the user each time claims no tool was made available, which doesn't match our server logs showing a successful tools/list response every time.
This a bit of a poor experience for a feature that GA'ed.
Can MS point to any working samples, github or otherwise?
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