Currently, Gluttony’s description reads
When this Pokemon has 1/2 or less of its maximum HP, it uses certain Berries early.
this doesn't explain what berries exactly Gluttony affects. Something like This Pokemon uses berries normally used at 1/4 or less of its maximum HP when it has 1/2 or less of its maximum HP.
would be more precise. That would be too long for the shortdesc I think, but it could be used as the longdesc, and there might be a different wording that I haven't thought of that could be short enough for the shortdesc.