I wonder about using the description metadata field (XMP-dc:Description) tag.

I think this is starting to get used, shown to users an editable field, in the smartphone image/video Gallery apps from both Apple and Google..

I managed to get someone working on a new open source Gallery app to add it to their app. Theres not yet been a release since it was added https://github.com/Lmh170/Android-Gallery-App