I wanted to use the Gmail smart compose feature in my project. I read many documents but no documents suggest anything related to the implementation of smart compose in Gmail API.
Attaching a link below about the small information about the autocomplete feature:
Unfortunately, this is not possible to do using the Gmail API.
The Gmail API using the client libraries works on a request-response basis, and these are not retrievable through a Gmail API method. In order to do this, there would need to be a request made each time the string the user is typing changes, which would use not only require a lot of network traffic, but would also make application running slow as many requests would be made.
On the flip side however, Google already knows about this, and a Feature Request for this has been made on their Issue Tracker. You can view this feature request here, to which you can click the star (☆) in the top left to let Google know more people want this feature to be implemented.