How can I call gmail api’s method without authentication everytime?

I want to use access token instead of authorization. I have get my token and stored it in local storage. Now I am saying, if user has token then do not need of authorization. just call the required method. But it says “API keys are not supported by this API. Expected OAuth2 access token or other authentication credentials that assert a principal. See https://cloud.google.com/docs/authentication”. How can I use access token in every Gmail method calling. Like for adding label, getting email messages in my DOM and all this stuff.
In short, I wanna get rid of every time authentication.