Groundmail MCP server in Google Antigravity

Connect Google Antigravity's agent to the Groundmail MCP server, and it can send email, check delivery, add and verify sending domains, and manage templates, webhooks and suppressions while it builds your app. Add one entry to mcp_config.json and sign in with your Groundmail account; there's no API key to paste.

Server URL: https://mcp.groundmail.dev/mcp (Streamable HTTP, OAuth) · All clients and the full tool list: MCP server

Add the server

Groundmail isn't in the MCP Store, so add it as a custom server:

In the editor's agent side panel, click … and choose MCP Servers.
Click Manage MCP Servers, then View raw config.
Add Groundmail to mcp_config.json:

JSON

{
  "mcpServers": {
    "groundmail": {
      "serverUrl": "https://mcp.groundmail.dev/mcp"
    }
  }
}

The global file is ~/.gemini/config/mcp_config.json and applies to every project. To add Groundmail to one project only, use .agents/mcp_config.json in that workspace.

In the Antigravity app, the same list is under Settings → Customizations → Installed MCP Servers (click refresh after editing the file). In the CLI, use /mcp.

Antigravity handles the OAuth sign-in for servers that support dynamic client registration, which Groundmail does, so you don't need an oauth block or a client ID. When the server connects, your browser opens on Groundmail: sign in, choose what the agent may do (full access, or less: Send only, Read only or a custom set of scopes) and approve.

The connection is listed under Settings → CLIs & agents in Groundmail, where you can revoke it.

Use it

Ask the agent, for example:

"List my Groundmail domains and tell me which aren't verified."
"Add a password reset email to this app with the groundmail SDK, and send me a test."
"Send a test email from noreply@mail.groundmail.dev to me and tell me if it was delivered."

Your app still needs its own GROUNDMAIL_API_KEY at runtime to send mail: the MCP connection is for the agent, not your deployed code. See Node.js.

Use an API key instead

For a machine where nobody can sign in in a browser, pass a key in a header. Create one at app.groundmail.dev/api-keys; a scoped key limits what the agent can do.

JSON

{
  "mcpServers": {
    "groundmail": {
      "serverUrl": "https://mcp.groundmail.dev/mcp",
      "headers": {
        "Authorization": "Bearer gm_your_key_here"
      }
    }
  }
}

Keep a workspace mcp_config.json with a key out of git.

Run it locally (stdio)

JSON

{
  "mcpServers": {
    "groundmail": {
      "command": "npx",
      "args": ["-y", "groundmail-mcp"],
      "env": {
        "GROUNDMAIL_API_KEY": "gm_your_key_here"
      }
    }
  }
}

Troubleshooting

Problem	Fix
The server doesn't appear	Check the JSON is valid and uses `mcpServers`, then refresh the server list.
It fails to connect	Use the full URL with `/mcp`. Antigravity needs Streamable HTTP; don't use `httpUrl` or an SSE URL.
`insufficient_scope` from a tool	The connection or key doesn't have that scope. Reconnect and grant it, or use a key with the scope.
Sends to other people are refused	Test sends go to your own account email. Sending to anyone else needs a verified domain: see Test sends and idempotency.

Other editors: GitHub Copilot (VS Code) · Zed · Warp · Cursor, Claude Code, Codex, Windsurf

Add the server

Sign in

Use it

Use an API key instead

Run it locally (stdio)

Troubleshooting