Here's a summary of the different calls available, if you are building your own client.
The API is accessed at the following URL (and alternatively without SSL):
| Panel | 
|---|
| https://api.textmarketer.co.uk/services/rest/<resource (see table)> | 
e.g., the credits resource can be accessed via the URL:
| Panel | 
|---|
| https://api.textmarketer.co.uk/services/rest/credits | 
There is also a sandbox service available via the URL (not available via SSL/https):
| Panel | 
|---|
| http://sandbox.textmarketer.biz/services/rest/ | 
See more about here.
Authentication is handled by passing your API username/password as GET/POST arguments, or you can use HTTP Basic Authentication.
See more on Authentication.