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.
GETGetItemID
https://api.steampowered.com/ITFPromos_440/GetItemID/v1/
NameValueTypeRequiredDescription
uint64 Yes The Steam ID to fetch items for
uint32 Yes The promo ID to grant an item for
POSTGrantItem
https://api.steampowered.com/ITFPromos_440/GrantItem/v1/
NameValueTypeRequiredDescription
uint64 Yes The Steam ID to fetch items for
uint32 Yes The promo ID to grant an item for