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_730/GetPlayerItems/v1/
NameValueTypeRequiredDescription
uint64 Yes The Steam ID to fetch items for
GETGetSchemav2
https://api.steampowered.com/IEconItems_730/GetSchema/v2/
NameValueTypeRequiredDescription
string NoThe language to return the names in. Defaults to returning string keys.
GETGetSchemaURLv2
https://api.steampowered.com/IEconItems_730/GetSchemaURL/v2/
GETGetStoreMetaData
https://api.steampowered.com/IEconItems_730/GetStoreMetaData/v1/
NameValueTypeRequiredDescription
string NoThe language to results in.