What is the AuthSub/OAuth scope?
The Documents List API uses the following scope: http(s)://docs.google.com/feeds/. In addition to this scope, to download Spreadsheets and PDFs you’ll need to request a token valid for http(s)://spreadsheets.google.com/feeds/ and http://docs.googleusercontent.com. Thus, it is recommended to use scope=http://docs.google.com/feeds/%20http://spreadsheets.google.com/feeds/%20http://docs.googleusercontent.com when requesting a new token.