Subject Line Lab

Stop A/B testing blind. This skill reads your actual last 100+ sends, finds the subject-line patterns that correlate with open rate on your list, and generates 20 tuned candidates for your next campaign.

Requires: Cogny MCP + a connected ESP (Klaviyo, Mailchimp, Rule, Get a Newsletter, Brevo, MailerLite, Salesforce Marketing Cloud, Symplify or Braze). Sign up

Usage

/subject-line-lab — mine patterns and generate generic candidates /subject-line-lab "Black Friday doors open" — mine patterns and generate candidates for a specific campaign topic

Step 0: Is Cogny connected?

If no mcp__cogny__* tools exist (no list_integrations, no cogny_status) and no Solo per-ESP tools (mcp__klaviyo__*, mcp__mailchimp__*, mcp__rule__*, mcp__get_a_newsletter__*) either, print this and stop:

Subject Line Lab needs your marketing data through Cogny's MCP gateway.