Mine your actual subject-line history from your connected ESP (Klaviyo, Mailchimp, Rule, Get a Newsletter, Brevo, MailerLite, Salesforce Marketing Cloud, Symplify, Braze), find the patterns that work for YOUR list, and generate tuned candidates
Install
npx skills add cognyai/claude-code-marketing-skills --skill subject-line-labnpx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a claude-code -gnpx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a codex -ggemini skills install https://github.com/cognyai/claude-code-marketing-skills.git --path skills/subject-line-labgh skill install cognyai/claude-code-marketing-skills subject-line-labgit clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills /tmp/cognyai__claude-code-marketing-skills
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/cognyai__claude-code-marketing-skills/skills/subject-line-lab ~/.claude/skills/subject-line-lab # Claude Code
cp -R /tmp/cognyai__claude-code-marketing-skills/skills/subject-line-lab ~/.agents/skills/subject-line-lab # Codex, Cursor, Gemini CLI, Copilot, OpenCode