Alt text and tooltips are incredibly important for accessibility. But to show a tooltip interaction in Figma, (afaik) you need to create a custom tooltip/find out as a component and then create a show/hide interaction on mouseover in the prototyping.
I would like to request that Figma allows for users to add tooltips to page elements, so that this functions per a standard tooltip — showing where the cursor hovers on the element, and with the user only needing to add the text (no need to create and hide a a text panel).