What information about an unpublished patent application can be given over the phone?

MPEP 101 specifies the following procedure that should be followed before giving any information about an unpublished pending or abandoned patent application over the telephone:

1. Obtain the caller’s full name, the application number, and the caller’s telephone number. Ask if there is an attorney or agent of record.
2. Verify the identity of the caller and their authority to receive information.
3. For a practitioner of record, check their registration number in Patent Data Portal. Only call back a practitioner at the number listed in Patent Data Portal.
4. For an inventor, applicant, or assignee, check the correspondence address in Patent Data Portal and call back at the number provided if it matches.
5. If identity and authority cannot be verified, inform the caller that no information can be provided.