Drafts cold-email subject lines from real signals, scored against what actually earns opens in B2B — not clickbait, not cleverness. Works with any sender; not locked to one provider.
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---
name: subject-line-writer
description: Drafts cold-email subject lines from real signals, scored against what actually earns opens in B2B — not clickbait, not cleverness. Works with any sender; not locked to one provider.
---
# Subject Line Writer
Draft a subject line based on the **signal**, the **persona**, and the **frame** — never on template inventory. Approve before use.
## Inputs
- Signal (what changed at the account in the last 90 days, e.g. hiring, expansion, tooling, compliance)
- Role of the recipient (who owns the consequence)
- Frame: question, observation, or data — pick one, not all three
- Optional: sender's proof anchor (a client type, a number, a category)
## Rules
1. **Signal over cleverness.** A fact about *what changed* beats wordplay about their business. "You opened 3 enterprise AE roles this quarter" survives; "You'll love this" doesn't.
2. **Specific numbers beat adjectives.** "$14,200 in ramp cost" > "big savings."
3. **Stop at 60 characters / ~7 words.** Mobile truncation is real; ambiguity is a tax.
4. **No spam triggers, ever.** Words like "free," "guarantee," "limited time," "opportunity," or fully capitalized words route to spam scoring on modern gateways.
5. **Match the sender.** The subject is a contract: what they open on must be answered inside. If you promised a question, don't pivot to a pitch.
## Approval
Show **3 ranked options** with a one-line read on each (why this frame, why this persona). Wait for selection, then optionally A/B top-two. Never proceed without pick.
## Scoring (rate each candidate 1–5)
- **Signal specificity** (1 = generic, 5 = "only true for them")
- **Promise boundedness** (1 = vague bait, 5 = you can answer it in 3 sentences)
- **Deliverability safety** (1 = trigger words, 5 = plain language)
Sum the 3; ship the highest. All 5s required before send recommendation.
## Voice rules
All skills in this bundle follow the shared voice rules: patterns broken, no AI vocabulary, specific numbers > adjectives. See `/references/voice-rules.md`.
