Email MCP Server for Cline
Wire marginal into Cline and let your agent generate subject line variants, launch A/B tests, and read lift metrics — all without leaving your editor.
Why run marginal as an email MCP server in Cline
Cline is an autonomous coding agent that lives in your editor and acts through MCP tools. By adding marginal as an email MCP server for Cline, you give that agent direct access to email experimentation — generating variants, launching managed sends, and pulling results into the same workflow where you write code.
Because marginal is hosted, there's no self-hosted MCP server to run or maintain. You point Cline at the marginal endpoint with a Bearer API key, and the four MCP tools become available to your agent immediately.
- No infrastructure — marginal runs as a hosted email MCP server
- Authenticate once with a Bearer key (marg_live_...)
- Keeps AI agent email marketing tasks inside your Cline session
- Free tier covers 100 experiments/month for testing
Configure the Cline MCP connection
Add marginal to your Cline MCP settings using the JSON config below. Replace the placeholder with your own key from the marginal dashboard. Once saved, Cline lists marginal's tools and your agent can call them when a task involves email.
- Endpoint: https://marginal.sh/mcp
- Registry name: sh.marginal/mcp
- Auth header: Authorization: Bearer marg_live_...
- Restart or reload Cline to pick up the new server
Tools your agent gets after the email MCP integration
Once the Cline MCP connection is live, your agent can chain marginal's tools to design and ship a subject line A/B test end to end. A typical flow: generate variants, launch the test on a managed send, then read open and click tracking with within-test lift metrics.
- generate_variants — draft competing subject lines for a test
- launch_test — start a managed send with split delivery
- get_results — open/click tracking and within-test lift metrics
- recommend_next — let the agent decide the next experiment
A practical Cline workflow
Ask Cline to draft and launch a subject line A/B test for an upcoming campaign. The agent calls generate_variants to produce candidates, launch_test to send them, and later get_results to surface the winner by lift. This makes email MCP integration a natural part of your release routine rather than a separate dashboard task.
See the marginal docs at https://marginal.sh/docs/ for tool schemas and example prompts, and the endpoint reference at https://marginal.sh/mcp.
Get started with marginal
marginal is a hosted email marketing MCP server at marginal.sh. Sign up free, create an API key, and connect https://marginal.sh/mcp from Cursor, Codex, or Claude Desktop.
- 100 experiments/month on the free tier
- Four MCP tools: generate_variants, launch_test, get_results, recommend_next
- Listed in the MCP Registry as sh.marginal/mcp