Windsurf MCP email server: run subject line tests from your editor
marginal is a hosted email marketing MCP server you can wire into Windsurf in minutes. Once connected, your agent can generate subject line variants, launch experiments, and read lift metrics without leaving the editor.
What the Windsurf MCP email server does
Windsurf speaks the Model Context Protocol, so it can call external tools through a registered MCP server. marginal exposes an email MCP server at https://marginal.sh/mcp that turns email experimentation into a set of agent-callable actions.
Instead of hand-coding send logic or juggling dashboards, you describe what you want in Windsurf and the agent drives the workflow through four focused tools.
- generate_variants — draft multiple subject line candidates for a campaign
- launch_test — start a subject line A/B test with a managed send
- get_results — pull open rates, click rates, and within-test lift
- recommend_next — get a data-backed suggestion for the next iteration
Why pair Windsurf with marginal
AI agent email marketing only works when the agent can both write copy and measure how it performs. marginal closes that loop: variants generated in one step are tested and scored by the same server, so Windsurf can reason over real engagement data.
Because marginal is fully hosted, there is no self-hosted MCP server to deploy or maintain. You authenticate with a Bearer API key (marg_live_...) and start running experiments immediately.
- Subject line A/B test orchestration handled server-side
- Open and click tracking with within-test lift metrics
- Free tier covering 100 experiments per month
- Works alongside other clients like Cursor, Claude Code, Cline, and Zed
A typical workflow in Windsurf
Once the marginal MCP server is registered in Windsurf, a single prompt can move from idea to measurable result. The agent chains the tools so you stay in flow.
- Ask Windsurf to generate variants for an upcoming newsletter subject line
- Launch a test against your audience with launch_test
- Check get_results after the send to compare opens and clicks
- Let recommend_next propose the winning direction for your follow-up
Getting set up
Add marginal as an MCP server in Windsurf using the endpoint https://marginal.sh/mcp and your API key. The registry identifier is sh.marginal/mcp.
Full configuration steps and tool references live in the docs at https://marginal.sh/docs/, so you can confirm the exact JSON your Windsurf version expects.
- Endpoint: https://marginal.sh/mcp
- Registry: sh.marginal/mcp
- Auth: Bearer API key (marg_live_...)
- Docs: https://marginal.sh/docs/
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