Google Developers has a star rating option and a Send Feedback button at the top and bottom of each page. You can rate or submit feedback.

Send feedback ☆☆☆☆☆.

The feedback feature at the bottom of the page:

Was this page helpful? ☆☆☆☆☆ Send feedback.

When you hover over each star, the rating describes itself as Unusable, Poor, Ok, Good, or Excellent.

Good documentation ★★★★☆.

When you click the Send Feedback button, a modal appears to submit documentation feedback or product feedback:

Send feedback about this page (documentation feedback) or Sheets API (product feedback).

When you click documentation feedback, the modal allows you to build a screenshot to center on the problem area. You can also describe your feedback in the text area:

Send feedback. Have feedback? We'd love to hear it, but please don't share sensitive information.

When you click product feedback, the link brings you to an external issue tracking site to submit your product feedback:

IssueTracker, Create Issue.