By default Attendant Pro interfaces with Skype for Business at the  Skype for Business Client SDK level for core functionality.

Attendant Pro can also interface with other back end Microsoft and 3rd party services if they are available. Below is a list.

Access Control
What it accesses
Skype for Business Client SDK mandatory Core functionality of Attendant Pro
Landis Technologies Web Service mandatory Enables easy retrieval of registration keys & application metrics/error logs

Exchange Web Services configurable MWI: Exchange UM Voicemail MWI (read), Advanced Search Contact List Provider: Global Address Book (read), Contact Notes: Exchange Contact List (read/write), Advanced Search Contact List Provider: Public Folders (read),
UCWA configurable Change My forwarding  (read/write)
Lync/Skype for Business RGS Web Service
uses if available
Show RGS Agent Group status (read)
SEFAUtil Server Enterprise
uses if available
3rd party. Only applicable if installed. See application documentation.