Power Platform Community Forum Thread Details

Copilot Studio connects to MCP servers using the Model Context Protocol (MCP) over HTTP. During connection, Copilot Studio sends HTTP POST requests to the configured MCP endpoint to establish the session and retrieve available tools and resources. In your case, the configured /sse endpoint does not allow POST requests, so the server returns “405 Method Not Allowed.” Because the endpoint only supports GET (typical for basic SSE setups), the MCP handshake fails and Copilot Studio cannot load tools. This is not a Copilot Studio bug; it is a server-side transport configuration issue. The MCP endpoint must accept HTTP POST requests and correctly implement the MCP HTTP transport specification over HTTPS for the connection to succeed.

Official References:

Copilot Studio – Add MCP server to agent:
https://learn.microsoft.com/en-us/microsoft-copilot-studio/mcp-add-existing-server-to-agent
Add tools and resources from a Model Context Protocol (MCP) server to your agent

What Must Be Fixed:

Ensure your MCP server supports HTTP POST for session initialization.
Implement the MCP HTTP transport exactly as defined in the MCP specification.
Do not expose only a GET-based SSE endpoint.
Deploy to a stable HTTPS endpoint (Azure Container Apps is recommended for streaming workloads).

Summary: