GarphenGate Subject Line Tester
Free gateway skill from the Newsletter Chief bundle by GarphenGate.
Five subject line variants for a finished issue, ranked with reasons a human can argue with, plus the preview text that completes each one.
Procedure
- Read the issue first (or its summary). The subject line is a promise; the tester must know what the issue can actually pay off.
- Generate five variants across mechanics: plain-benefit statement, curiosity with payoff, specific number or detail, question the reader is asking themselves, and personal or story-led. All five must be honest about the contents.
- Pair each with preview text that extends the promise instead of repeating the subject or leaking "View in browser".
- Rank all five with a one-line reason each, judged against: match to this issue's actual strength, clarity at a phone-width glance, and fit with the user's past subject style if known. Reasons cite the issue, never generic "curiosity performs well" lore.
- Name the risk on the top pick — every subject has one (too plain, too cute, over-promises) — so the user chooses with eyes open.
Output
SUBJECT TEST — <issue title/date>
1. "<subject>" + preview: "<text>" — why ranked here: <reason>
... (5, ranked)
Top pick risk: <one line>
House style note: <fits past sends? one line>
Rules
- Never write a subject line the issue cannot pay off; a great open rate on a broken promise raises the next issue's ignore rate.
- Never use fake urgency, fake personalization, or "RE:"/"FWD:" deception; these are banned regardless of performance.
- All-caps and multiple exclamation marks are out; one emoji at most, and only if the user's past sends use them.
- Rankings must cite the specific issue; a reason that could apply to any newsletter is not a reason.
Degradation
With no issue text provided, ask for a two-line summary of the lead item and generate against that, marking the ranking LOW CONFIDENCE. With no history of past subject lines, skip the house-style ranking factor and note that A/B testing inside the user's platform is the real judge.
Like this? This is the free gateway skill for Newsletter Chief by Moltline Studio. The paid listing: https://www.agensi.io/skills/newsletter-chief-persona