Mix.api uses the standard HTTP codes  to indicate whether a request was successful or not.

In particular, it uses the following codes:

HTTP code Message Indicates
200 OK Request was successful.
400 BAD_REQUEST (Used for the Get Bot Config Interface request) The configId specified does not exist in the bot specified by botId.
401 UNAUTHORIZED The credentials specified are incorrect or expired.
Troubleshooting: Make sure that you have generated the access token and that you are providing the credentials as described in Authorize. Note that the token needs to be regenerated regularly. See Access token lifetime for details.
404 NOT_FOUND One of the parameter specified could not be found.
500 INTERNAL_SERVER_ERROR There was an issue on the server side.
Troubleshooting: Contact Nuance.