The lowest overhead call that also exercises the Atmos authentication process is getServiceInformation().  
I use the Java binding for the Atmos REST API. My tool allows users to enter their atmos credentials in order to access their storage. I'd like to verify that the credentials have been entered correctly (so the user can correct them if not).  Which API call is suitable to do this? It should be inexpensive, always fail with wrong credentials, and always succeed with correct credentials.  Thanks, Carsten
How to verify user crdentials