Some elements in API documentation would benefit from tooltips (title attributes):

 - The input fields for search and TOC filtering are sometimes not big enough to display the entire placeholder text. Showing the placeholder text as tooltip when hovering over the input field would be helpful.

 - The links in the breadcrumb navigation only show module, package, and class names. We could improve the links by showing tooltips that describe the kind of element, such as "module x", "package y", or "class Z".