This web page is a guide for developers on the transition from Google's Contacts API to People API, since the former became obsolete on January 19, 2022. It informs of the equivalent functions in the People API, including some changes in scopes, endpoints, and fields. A notable adjustment is that 'Other Contacts' are now read-only, with restricted data access for administrators.
Developer’s Guide - Portable Contacts API - Google Code
http://code.google.com/apis/contacts/docs/poco/1.0/developers_guide.html#CreatingAccount