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.
UNDOCUMENTEDClaimBadgeReward
https://api.steampowered.com/ICSGOTournaments_730/ClaimBadgeReward/v1/
GETGetTournamentFantasyLineup
https://api.steampowered.com/ICSGOTournaments_730/GetTournamentFantasyLineup/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
uint64 Yes The SteamID of the user inventory
string Yes Authentication obtained from the SteamID
GETGetTournamentItems
https://api.steampowered.com/ICSGOTournaments_730/GetTournamentItems/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
uint64 Yes The SteamID of the user inventory
string Yes Authentication obtained from the SteamID
GETGetTournamentLayout
https://api.steampowered.com/ICSGOTournaments_730/GetTournamentLayout/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
GETGetTournamentPredictions
https://api.steampowered.com/ICSGOTournaments_730/GetTournamentPredictions/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
uint64 Yes The SteamID of the user inventory
string Yes Authentication obtained from the SteamID
POSTUploadTournamentFantasyLineup
https://api.steampowered.com/ICSGOTournaments_730/UploadTournamentFantasyLineup/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
uint64 Yes The SteamID of the user inventory
string Yes Authentication obtained from the SteamID
uint32 Yes Event section id
uint32 Yes PickID to select for the slot
uint64 Yes ItemID to lock in for the pick
uint32 Yes PickID to select for the slot
uint64 Yes ItemID to lock in for the pick
uint32 Yes PickID to select for the slot
uint64 Yes ItemID to lock in for the pick
uint32 Yes PickID to select for the slot
uint64 Yes ItemID to lock in for the pick
uint32 Yes PickID to select for the slot
uint64 Yes ItemID to lock in for the pick
POSTUploadTournamentPredictions
https://api.steampowered.com/ICSGOTournaments_730/UploadTournamentPredictions/v1/
NameValueTypeRequiredDescription
uint32 Yes The event ID
uint64 Yes The SteamID of the user inventory
string Yes Authentication obtained from the SteamID
uint32 Yes Event section id
uint32 Yes Event group id
uint32 Yes Index in group
uint32 Yes Pick ID to select
uint64 Yes ItemID to lock in for the pick