API (Application Programming Interface) - this set of features provided by the service for third party developers.
At the moment the service sends in flash projects through flashvars the following variables:
pid - unique ID of the article
uid - unique user ID
ulogin - user login
uphoto - user avatar (PNG, 180X180)
sig - md5 from strings pid+'_'+secret_key_project+'_'+uid
Example code ActionScript 3.0 - sources.