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.
GETGetCMList
https://api.steampowered.com/ISteamDirectory/GetCMList/v1/
NameValueTypeRequiredDescription
uint32 Yes Client's Steam cell ID
uint32 NoMax number of servers to return
GETGetCMListForConnect
https://api.steampowered.com/ISteamDirectory/GetCMListForConnect/v1/
NameValueTypeRequiredDescription
uint32 NoClient's Steam cell ID, uses IP location if blank
string NoOptional CM type filter
string NoOptional Steam Realm filter
uint32 NoMax number of servers to return
uint32 NoDesired connection priority
GETGetSteamPipeDomains
https://api.steampowered.com/ISteamDirectory/GetSteamPipeDomains/v1/