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.
UNDOCUMENTEDCanClaimItem
https://api.steampowered.com/ISaleItemRewardsService/CanClaimItem/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
string Nolanguage short name
UNDOCUMENTEDPOSTClaimItem
https://api.steampowered.com/ISaleItemRewardsService/ClaimItem/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
string Nolanguage short name
https://api.steampowered.com/ISaleItemRewardsService/GetClaimedSaleRewards/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
int32 Noenum
string No
bool No
https://api.steampowered.com/ISaleItemRewardsService/GetCurrentDefinition/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
int32 Noenum
string No
bool No
https://api.steampowered.com/ISaleItemRewardsService/GetRewardDefinitions/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 No
UNDOCUMENTEDPOSTSetRewardDefinitions
https://api.steampowered.com/ISaleItemRewardsService/SetRewardDefinitions/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
int32 Noenum
CSteamItemRewardDefinition[] No
uint32 No
uint32 No
uint32 No
uint32 No
uint32 No
uint32 No
int32 Noenum