The TrustedQSL library API is divided into several groups:

Certificate Handling API - Request, load and retrieve digital certificates
Data API - Manage station-location data and produce signed data records
Converter API - Convert and sign ADIF and Cabrillo log files
Utility API - Functions to operate on objects, set system parameters, and report errors
Signing API - Low-level digital signing
ADIF API - Low-level parsing and creation of ADIF files
Cabrillo API - Low-level parsing of Cabrillo files.

Most of the library functions return an integer value that is zero if there is no error and 1 if there is an error. The specific error can be determined by examining tQSL_Error and, possibly, tQSL_ADIF_Error, tQSL_Cabrillo_Error, tQSL_ErrorFile and tQSL_CustomError. The tqsl_getErrorString() and tqsl_getErrorString_v() functions can be used to get error text strings.