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.
UNDOCUMENTEDGetGamePlayerCounts
https://api.steampowered.com/IDOTA2CustomGames_2305270/GetGamePlayerCounts/v1/
UNDOCUMENTEDGetPopularGames
https://api.steampowered.com/IDOTA2CustomGames_2305270/GetPopularGames/v1/
UNDOCUMENTEDGetSuggestedGames
https://api.steampowered.com/IDOTA2CustomGames_2305270/GetSuggestedGames/v1/
UNDOCUMENTEDGetWhitelist
https://api.steampowered.com/IDOTA2CustomGames_2305270/GetWhitelist/v1/
UNDOCUMENTEDGetWorkshopVoteQueue
https://api.steampowered.com/IDOTA2CustomGames_2305270/GetWorkshopVoteQueue/v1/