Any tools that are not on the approved list or have been approved or are being looked into are a violations of the in-game rules and can result in a ban. So make sure you're not using any add-ons that may "better" you in-game playing experience that limits the amount of clicks you have to do or does the work for you in general.
Greasemonkey, or a similar browser extension, is needed in order to make scripts and add-ons possible for certain browsers, most notably Firefox. It doesn't do anything on its own, really.