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.
PUBLISHERPOSTCallPublisherKey
https://partner.steam-api.com/ITestExternalPrivilegeService/CallPublisherKey/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
PUBLISHERPOSTCallPublisherKeyOwnsApp
https://partner.steam-api.com/ITestExternalPrivilegeService/CallPublisherKeyOwnsApp/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes