This is to be used for a Psychiatric Diagnostic Evaluation - aka an initial diagnostic interview exam that does not include any medical services.  You need to note the patient’s chief complaint, history of present illness, family and psychosocial history, and complete mental status examination.  Keep in mind that Medicare will pay for only one 90791 per year for institutionalized patients  - that is, of course, unless your provider has established medical necessity for more work.