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.
GETGetPlayerItems
https://api.steampowered.com/IEconItems_620/GetPlayerItems/v1/
NameValueTypeRequiredDescription
uint64 Yes The Steam ID to fetch items for
GETGetSchema
https://api.steampowered.com/IEconItems_620/GetSchema/v1/
NameValueTypeRequiredDescription
string NoThe language to return the names in. Defaults to returning string keys.