A meta description doesn't move your ranking. Google says this outright, and testing backs it up — you can rewrite one all day and your position in the results won't budge. What it does move is whether a person scanning ten blue links stops on yours. That's a click-through problem, not an SEO problem, and it gets solved with different tools than keyword research.
The character limit isn't really 160
Google renders descriptions by pixel width, not character count, so a sentence full of narrow letters (i, l, t) fits more than one full of wide letters (m, w, capital letters). In practice, 150–155 characters is the safer target before truncation starts cutting mid-word. Write the sentence, then paste it into our character counter and trim from the end, not the middle — the last clause is usually the weakest part anyway.
Three rewrites, with the actual before and after
Before: "Learn about our JSON formatter tool and how it can help you format JSON data online for free."
After: "Paste messy JSON, get indented output in one click. Catches trailing commas and bad brackets before your API call does."
The first version repeats "JSON" three times and tells you nothing a title tag hasn't already said. The second names a specific failure mode (trailing commas) that someone searching "json formatter" has almost certainly hit.
Before: "Our password generator creates strong, secure passwords for all your accounts instantly."
After: "Generate a 20-character random password in your browser. Nothing is sent anywhere — check the network tab if you don't believe us."
The second version answers the objection a privacy-conscious searcher actually has, instead of restating the headline.
The one habit that matters more than wording
Open Search Console and look at your actual click-through rate for a query before rewriting anything. A page ranking position 3 with a 1% CTR has a description problem worth fixing. A page ranking position 9 with the same CTR probably has a ranking problem no description will fix — don't waste an afternoon polishing copy nobody scrolls far enough to read.