Zed Editor MCP Email: Subject Line Testing from Your Editor
If you live in the Zed editor, you can wire up marginal's email MCP server and run subject line experiments straight from your AI assistant — no context switching to a marketing dashboard.
Why run email tests from Zed?
Zed ships with native MCP support, so any agent you drive inside the editor can call external tools over the Model Context Protocol. marginal is a hosted email MCP server, which means Zed talks to a single remote endpoint and gets back generated variants, send results, and lift metrics.
For growth engineers who already script campaigns in code, the Zed editor MCP email workflow keeps experimentation close to where you build. You describe the test in natural language, the agent calls the tools, and you stay in your editor.
- No marketing UI to learn — it's all driven from your agent prompt
- Hosted server at https://marginal.sh/mcp, nothing to self-host
- Bearer API key auth keeps configuration to a single secret
What the MCP tools do
marginal exposes four MCP tools that map cleanly to a subject line A/B test loop. An AI agent in Zed can chain them in one conversation.
- generate_variants — draft multiple subject line options for one campaign
- launch_test — start a managed send and split the audience across variants
- get_results — pull open and click tracking plus within-test lift metrics
- recommend_next — let the agent suggest the next experiment to run
A typical AI agent email marketing loop
Once connected, your Zed agent can run an end-to-end experiment. Ask it to generate variants for a launch announcement, launch a test against a segment, then circle back later to read results and decide a winner.
Because marginal reports within-test lift rather than raw aggregate numbers, the agent gets a clean signal it can act on when calling recommend_next. That makes AI agent email marketing iterative instead of guesswork.
- Generate 4 subject lines, launch a split, and check back in a day
- Compare open and click rates with lift attributed inside the test
- Free tier covers 100 experiments/month to validate the workflow
Getting set up
Add marginal as an MCP server in Zed's settings, pointing at the marginal endpoint and supplying your Bearer key (it starts with marg_live_). After that, your agent can discover and call the email tools automatically.
Full configuration steps and tool schemas live in the marginal docs at https://marginal.sh/docs/, and the MCP overview is 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