Every status code except 200 is considered an error and you will get a message in the response JSON explaining the error.
Sample non-200 response:
API Reference
Status Codes
PearCheck uses standard HTTP response codes to indicate the success or failure of an API request. Most of our failure error codes will contain a message on why the request failed. uses standard HTTP response codes to indicate the success or failure of an API request. Most of our failure error codes will contain a message on why the request failed.