One line under a show-page tab heading saying what the tab shows and how something gets into it — with the way to do that as an inline link when it happens on another page.
Every tab on the contact and company pages is fed from somewhere else (a contact's edit form, a member's interaction log, the catalogue's item form, the activity log), and without this line an empty tab read as broken rather than as "nothing here yet, and here is where to add it".
Summary
Functions
The explanatory line. text is the sentence; the :action slots render
after it as links (each slot takes navigate and its label as content).