The parameterCheck function allows you to verify that a parameter is valid for an API call without actually making an API call. This can be used to validate user input or to confirm that the data you are sending is the data you think you are sending. You can validate either as a specific parameter in a specific function or against a general parameter type.
Check whether a particular string will be accepted as the 'cli' option in numberOverlay:
Note, just because a parameter is valid does not mean the API call will be successful. For example you may use this function to prove that 09123456789 is a valid destination number, but if you do not have permission to overlay premium rate numbers then providing it in a request to numberOverlay will still fail.