Use it as an editor, not an author. AI-written applications fail for a specific and predictable reason: the model doesn't know anything about you, so it produces confident, well-structured, completely generic text — and generic is the exact failure mode a cover letter exists to avoid.
What happens when you let it write from scratch: 'I am a passionate and detail-oriented professional with a proven track record of delivering results in fast-paced environments.' That sentence is grammatically perfect, says nothing, and recruiters see fifty of them a day. It reads as AI not because of a detectable watermark, but because it's content-free.
The division of labour that works:
**You provide the substance** — the specific projects, the numbers, the actual problem you solved, the reason you want this particular job. Nobody else has this, and it's the only part that persuades.
**AI helps with:**
1. **Tightening.** Paste your rambling paragraph, ask it to cut it to 60 words without losing the specifics. Genuinely good at this.
2. **Fixing grammar and flow**, especially valuable if English isn't your first language. This is a legitimate levelling of the field, not cheating.
3. **Turning duties into achievements.** Give it 'I handled customer support tickets' plus the real numbers, and ask for an achievement-framed version. 'Resolved 40+ daily support tickets, cutting average response time from 6 hours to 90 minutes' — where the numbers came from you.
4. **Tailoring.** Paste the job description and your resume, ask which of your experience maps to their stated requirements and what you've under-emphasised. This is the highest-value use.
5. **Critique.** 'You're a hiring manager for this role. What's weak here? What would make you reject it?' Much better than asking it to write.
The non-negotiables:
- **Never let it invent anything.** It will happily add plausible achievements. Every claim must be true and defensible in an interview.
- **Rewrite the output in your own voice.** If you couldn't say the sentence out loud without cringing, change it. The interview will compare the letter to the person.
- **Cut every adjective that isn't evidenced.** 'Passionate', 'dynamic', 'results-driven' — delete them all and replace with a specific fact.
One detail worth knowing: recruiters largely aren't running detectors on applications, and most wouldn't care if a candidate polished their grammar. What they screen out is *generic* — so the risk isn't being caught, it's being forgettable.