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HTTP status: 400

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Error message

(or, when no OAuth metadata is found at all: “Could not discover the server’s OAuth authorization metadata.”)

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When this error occurs

POST /mcp-connections only performs self-service OAuth via Dynamic Client Registration (DCR). It probes the server for authorization metadata (PRM / RFC 9728 → RFC 8414 → OIDC discovery) and a registration_endpoint. You get this error when that can’t be resolved — either the server isn’t an OAuth-protected resource, or it advertises OAuth but not DCR.

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You may not need a connection at all

If the error notes that tools are available without authorization — e.g. “3 tool(s) are available without authorization” — the server is usable open: skip the connection entirely and add its URL to mcp_servers[] with no connection_id. Some servers (Mintlify-hosted docs MCPs, for example) are open by default and only enable DCR when they host gated content.

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How to fix

  • Only need the open tools? Add the URL to mcp_servers[] without a connection_id.
  • If the server requires auth but only registers clients manually (static client id/secret), that flow isn’t supported here — obtain access out of band.
  • If you expected auto-connect, confirm the server implements OAuth DCR per the Model Context Protocol authorization spec.