Finding the Help page for a Tool isn’t as easy as for Reports or Gramplets. (Every Report has a Help button in the options dialog. Grampets have a Help button when detached/undocked from the sidebar/bottombar/dashboard.)
Some of the tools don’t even pop-up a dialog before performing their task. So there is no obvious place for a Help button from the Tools menu. (The Tools Selection and Reports Selection dialogs might be future location for a Help button.)
Although there is an indexed page of built-in Tool documentation, Gramps does NOT have a visible indicator for which menu items are addons. So it is hard to know whether to check built-in Report list or add-on list of Tools in the Wiki Manual. A collated alphabetical list of built-in (with add-ons as of June 2021) Tools linked to their Help pages has been posted in the forum.