This does not exist but it should. Since the macro icon command is /macroicon or /micon, for consistency the tooltip should be /macrohelp or /mhelp (since tooltips are officially called “item help” and “action help” in menus).

Some might suggest that /micon should include the tooltip automatically, and this would be mostly fine, but a separate /mhelp would allow one to give a macro a particular icon but show the help for a different action or item.