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, or Get a Newsletter). 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

Prerequisites Check

Detect which ESP is connected. Check both namespaces (Cloud-aggregated via mcp__cogny__<svc>__* and Solo/Lite per-ESP via mcp__<svc>__*):

• Klaviyo → mcp__cogny__klaviyo__* or mcp__klaviyo__*
• Mailchimp → mcp__cogny__mailchimp__* or mcp__mailchimp__*
• Rule → mcp__cogny__rule__* or mcp__rule__*
• Get a Newsletter → mcp__cogny__get_a_newsletter__* or mcp__get_a_newsletter__*