Email MCP Documentation
This guide explains how the marginal email MCP server works, which tools it exposes, and where to find detailed references. If you searched for email MCP documentation to wire up AI agent email marketing, start here.
What the email MCP server does
marginal is a hosted email marketing MCP server. Instead of running infrastructure yourself, your AI agent connects to a single endpoint and gains the ability to draft, test, send, and measure email campaigns through the Model Context Protocol.
The full email MCP documentation lives at https://marginal.sh/docs/, but the core idea is simple: every email operation is exposed as an MCP tool your agent can call directly.
- Endpoint: https://marginal.sh/mcp
- Registry name: sh.marginal/mcp
- Auth: Bearer API key in the form marg_live_...
- Hosted only — there is no self-hosted server to maintain
The four MCP tools
The marginal email MCP server keeps its surface area small so agents can reason about it reliably. Each tool maps to one step in a typical experiment loop.
- generate_variants — produce candidate subject lines for a subject line A/B test
- launch_test — start a managed send and split delivery across variants
- get_results — read open and click tracking plus within-test lift metrics
- recommend_next — suggest the next variant or winning subject to scale
A typical agent workflow
Because the tools are sequenced, an AI agent can run an end-to-end experiment without human glue code. The documentation describes the request and response shape for each call, including how lift is computed inside a single test.
A common loop looks like this:
- Call generate_variants to get several subject line candidates
- Use launch_test to send them as a subject line A/B test
- Poll get_results for opens, clicks, and lift
- Call recommend_next to decide what to send to the remaining list
Getting started and limits
marginal connects to MCP clients including Cursor, Claude Desktop, Claude Code, OpenAI Codex, Windsurf, Cline, Continue, and Zed. Point any of them at the endpoint with your Bearer key and the tools appear automatically.
The free tier covers 100 experiments per month, which is enough to validate AI agent email marketing workflows before scaling. For full schemas, error handling, and examples, see the email MCP documentation at https://marginal.sh/docs/.
- Free tier: 100 experiments/month
- MCP endpoint: https://marginal.sh/mcp
- Full reference: 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