The rules it checks
- No spaces after commas.
water,habitandwater, habitindex the same words; the space costs a character. - Don’t repeat the name or subtitle. Words there are already indexed. Repeating them in the keyword field wastes the space.
- Single words over phrases. Apple combines words across the three fields, so
water,trackercan match “water tracker” and “tracker for water”. - Skip filler. Words like “app” or “free” match almost everything and rarely win a search.
- Localize the field. Each localization has its own 100 characters, and some storefronts index more than one language. That is extra room, not a duplicate.
These are character-efficiency checks, not ranking predictions. Change one thing, then compare impressions over equal, fully reported weeks before deciding it worked.