MCP errors - Will This Person Answer

Tool result

{
  "isError": true,
  "content": [{
    "type": "text",
    "text": "INSUFFICIENT_CREDITS: Not enough credits. 5 needed, 3 available."
  }]
}

Error codes

Code	Meaning	REST equivalent
`INVALID_INPUT`	A field is missing or did not pass validation, or no request has that id.	400, 404
`AUTH_FAILED`	The API key is missing, wrong or revoked.	401
`INSUFFICIENT_CREDITS`	Not enough credits. Don’t retry until credits are added.	402
`DUPLICATE_REQUEST`	The idempotency key was used for different content, or the first request is still running.	409
`RATE_LIMITED`	Over 60 requests in 60 seconds.	429
`SERVICE_UNAVAILABLE`	The lookup could not run right now. Nothing was charged. Try again.	503
`INTERNAL_ERROR`	Something went wrong on our side.	500

A number we could not check is not an error. It comes back in a normal result with status: "unable_to_check" and a reason.