Don't use tooltips

Description Impossible to define
Role Poorly supported
Relationships None
State Unclear
Focus Unclear
Action Undefined

Why we don't use tooltips:

Tooltips are extremely difficult to implement. The specific WAI-ARIA guidance isn't clear, so it's impossible to create success criteria.

Tooltips are often indicative of poor UX design. If there is important content that is required to understand the UI, the tooltip is a sub optimal approach to helping the user.