"Tooltips with obvious or redundant text are not beneficial to users. If you can’t think of particularly helpful content, don’t offer a tooltip. Otherwise, you’ll just add information pollution to your UI and waste the time of any users unlucky enough to activate that tooltip. Tooltips are microcontent, — short text fragments intended to be self-sufficient. Your copy can be single- or multiple-line long as long as it’s relevant and it does not block related content."