This page is just a reference of all the known Steam APIs, I do not know how they work. Please do not email me with questions.
PUBLISHERGETCheckUserStatus
https://partner.steam-api.com/ISteamSpecialSurvey/CheckUserStatus/v1/
NameValueTypeRequiredDescription
click to setstring Yes access key
uint32 Yes appid of game
uint32 Yes ID of the survey being taken
uint64 Yes SteamID of the user taking the survey
string Yes Survey identity verification token for the user
PUBLISHERPOSTSetUserFinished
https://partner.steam-api.com/ISteamSpecialSurvey/SetUserFinished/v1/
NameValueTypeRequiredDescription
click to setstring Yes access key
uint32 Yes appid of game
uint32 Yes ID of the survey being taken
uint64 Yes SteamID of the user taking the survey
string Yes Survey identity verification token for the user