Should tooltips be used on Text/Links?

1. When should you not use tooltip?
2. Can tooltips have links?
3. Where should tooltips be placed?

When should you not use tooltip?

1. Don't use tooltips for information that is vital to task completion. Users shouldn't need to find a tooltip in order to complete their task.

Can tooltips have links?

Because the tooltip itself never receives focus and is not in the tabbing order, a tooltip can not contain interactive elements like links, inputs, or buttons.

Where should tooltips be placed?

Tooltips should be placed near the object being hovered, usually at the pointer's tail or head if possible. However, tooltips should never be placed in a way that interferes with what the user is doing. Don't: cover the object the user is about to view or interact with.