HTTP 400
invalid_request_bodyInvalid MCP request body
The MCP HTTP request body could not be read or decoded.
Resolution
Send a valid MCP JSON-RPC request body.
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.