Question on feet

New to tagging, my question is how much focus on feet does it need to be tagged as something such as barefoot? Does it need to be the focus, or is having barefeet/foot in the image good enough to tag it as so?

Per the wiki:

When one or both of a character's feet are prominently displayed or detailed. Add foot focus when the feet are the main subject or focus of the image.

This does not include feet fully covered by shoes. Feet covered by sandals, socks, thighhighs, or pantyhose still count.

So if you can see the feet distinctly illustrated in some way, add feet. If nothing's worn on them, add barefoot. If the image is something foot fetishists would probably get a kick out of, add foot focus.