I am using google oauth in my application, and I need to find out if that user is the admin of that domain. How do I do that?
You can use the Admin SDK Directory API's users.list() call while specifying a
query parameter of
isAdmin=true to pull a list of all super admin users in the Google Apps domain.
Update: with the new roleAssignments.list() call you can determine admin rights for super and delegated admins which offers a greater level of detail about which users have which admin privileges.