Most Google APIs are not Google Data APIs. This Google Data APIs documentation applies only to a few APIs, as described in the GData API Directory.
About the Google Data ProtocolSome services at Google provide external access to data and functionality through APIs that utilize the Google Data (GData) Protocol. The GData Protocol is a REST-inspired technology for reading, writing, and modifying information on the web. It supports two primary modes of access, AtomPub and JSON.
For information about Google APIs that implement the GData Protocol, along with a list of APIs that replace those that previously implemented the GData Protocol, see the GData API Directory.
For information about authorizing requests with a newer Google API, see the Google Identity Platform.