Cline MCP Email Marketing
If you live in Cline, you can run real email experiments without context-switching. Connect Cline to marginal's hosted email MCP server and let your AI agent draft subject lines, launch A/B tests, and pull results — all from chat.
Why pair Cline with an email MCP server
Cline is an agentic coding assistant, which makes it a natural fit for AI agent email marketing workflows. Instead of copying campaign ideas into a separate dashboard, you describe what you want and the agent calls marginal's MCP tools directly.
marginal is fully hosted, so there's nothing to deploy. You point Cline at the endpoint, supply a Bearer API key, and the four MCP tools become available as actions your agent can chain together.
- generate_variants — draft candidate subject lines from a brief
- launch_test — start a managed send with your variants
- get_results — pull open/click tracking and within-test lift
- recommend_next — get a data-backed suggestion for the next step
A subject line A/B test, end to end
A typical Cline MCP email marketing session looks like a short conversation. You give the agent your audience and goal, it proposes variants, you approve, and the test goes live.
Because marginal handles the managed send and tracking, the agent can come back later and read the lift between variants — no spreadsheet plumbing or manual export.
- Ask Cline to generate 4 subject line variants for a launch email
- Approve the set, then have it call launch_test to send
- After the test window, request get_results for opens, clicks, and lift
- Let recommend_next tell you which variant to scale
Connecting Cline to marginal
Cline supports MCP servers, so adding marginal is a matter of registering the endpoint and your API key. The endpoint is https://marginal.sh/mcp and auth uses a Bearer key that starts with marg_live_.
Once connected, the marginal tools show up in Cline alongside your other capabilities. You can verify the setup by asking Cline to list available tools or to run a quick generate_variants call. Full setup steps live in the docs at https://marginal.sh/docs/.
- Endpoint: https://marginal.sh/mcp
- Auth: Bearer API key (marg_live_...)
- Registry id: sh.marginal/mcp
- Free tier: 100 experiments per month to start
Where this fits in your workflow
The same marginal email MCP server that powers Cline also works in Cursor, Claude Code, Windsurf, Continue, Zed, and other MCP clients — so you can keep your subject line A/B test process consistent across tools.
For growth engineers, that means experiment logic lives next to your code and prompts. Iterate on a subject line A/B test the same way you'd iterate on a feature, and let the agent surface the winning variant when the data is in.
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