HTTP 415
unsupported_media_typeUnsupported media type
The MCP endpoint received an unsupported request content type.
Resolution
Send MCP JSON-RPC requests with Content-Type: application/json.
Response handling
Keep the response's request_id for diagnostics. Retry only transient 429 and 503 responses, using the rate-limit headers and exponential backoff with jitter. Correct 400, 401, and 403 requests before retrying.