The most common failure is not bad writing — it is redundancy. A letter that summarises your job history gives the reader nothing they did not already have, and the reader knows it within a sentence. A letter earns its place when it carries something the resume structurally cannot: why this role, why now, why the unusual thing on page one is a strength rather than a gap.

This tool checks for that specifically. It flags paragraphs that restate rather than add, openings that spend their most valuable sentence on a formality, and closings that ask for nothing. Then it shows you a version that does the job.

It matters most when your application is not self-explanatory: a career change, an employment gap, a relocation, a step down in title for a step up in scope, or an internal referral you need to name. In those cases the letter is doing work nothing else can do, and a weak one costs you the role.

For a straightforward application to a large employer with a heavily automated pipeline, the resume does most of the work and the letter is a formality. Knowing which situation you are in tells you how much effort the letter deserves — and the feedback here reflects that rather than treating every letter as equally critical.