For error checking, use error codes, not error messages.
Error messages do not change often, but it is possible.
Requests to the API are categorised by the different areas of functionality of the payment platform.
The API supports transaction processing and token processing with other areas planned. Different HTTP methods imply different operations, for example retrieval of information from the database is handled by the GET operation, while updates are handled by either POST or PUT requests as appropriate.
API response codes handle specific validation, system errors and invalid authentication details.