Hi Federico,
Let's start with the most basic call on that object. Do you get the same error when you invoke the
drive.about.get action? Can you post a screen shot of your process flow?
The
fields data item is a general purpose data item that Google exposes on all of their Drive actions. You can use it to specify which specific fields you want Google to include in the response to any method call. You can find the generic Google description of it at the following link:
https://developers.google.com/drive/api/v3/fields-parameterBe aware that each action on the Drive API has different possible return fields though, so you'd have to look at the documentation of whatever method you want to call to see what fields are available if you think you want to try and customize the return.
Cheers,