Subject Line Lab
Generate and screen cold email subject lines against truncation, spam triggers and the preview text they create.
Free
Works with the AI tools you already use
Claude Code
Cursor
Codex CLI
GitHub Copilot
Gemini CLI+17 moreClaude CodeCursorCodex CLIGitHub CopilotGemini CLI
VS Code
Windsurf
Manus+14 moreSee it in action
You say
Write subject lines for this email to VPs of Sales about our new lead data tool. The first line is: I noticed your team is hiring three new SDRs this month.
Your agent does
| Subject | 30ch | 45ch | Preview | Test | | :--- | :--- | :--- | :--- | :--- | | Question about the 3 SDRs | Question about the 3 SDRs | Question about the 3 SDRs | I noticed your team... | Specificity | | SDR hiring | SDR hiring | SDR hiring | I noticed your team... | Brevity |
About this skill
Generate and screen cold email subject lines against truncation, spam triggers and the preview text they create. Use when someone needs subject lines, has low open rates, or wants to test subject variants.
Every free skill sits on a 30 day review cycle. Fixes and improvements ship as repo updates. Free forever. The premium version of this workflow lives in the Cold Email System Pack at mambabuilt.com.
How to install
Drop the file into your AI Agent. Works with Claude, Cursor, ChatGPT, and 20+ more.
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