---
title: MCP Server
description: Learn how to use the MCP Server to send emails with Reloop.
---
> For the complete documentation index, see [llms-docs.txt](/llms-docs.txt) or the site index [llms.txt](/llms.txt). Full docs corpus: [llms-full-docs.txt](/llms-full-docs.txt). Prefer markdown URLs (append `.md`) for agent consumption. Product skill: [skill.md](/skill.md).
## What is an MCP Server?
The Model Context Protocol (MCP) is an open standard that lets AI models connect to external tools and data sources. An MCP server acts as a bridge between your AI agent and the Reloop API, allowing the agent to send emails, manage contacts, handle domains, and more — all through natural language.
## What can Reloop's MCP Server do?
The [Reloop MCP Server](https://github.com/reloop-labs/reloop-mcp) exposes the full Reloop API as MCP tools:
- **Emails** — Send, list, get, cancel, update, and batch send emails. Supports HTML, plain text, attachments (local file, URL, or base64), CC/BCC, reply-to, scheduling, tags, and topic-based sending.
- **Received Emails** — List and read inbound emails. List and download received email attachments.
- **Contacts** — Create, list, get, update, and remove contacts. Manage segment memberships and topic subscriptions. Supports custom contact properties.
- **Broadcasts** — Create, send, list, get, update, and remove broadcast campaigns. Supports scheduling, personalization placeholders, and preview text.
- **Domains** — Create, list, get, update, remove, and verify sender domains. Configure tracking, TLS, and sending/receiving capabilities.
- **Segments** — Create, list, get, and remove audience segments.
- **Topics** — Create, list, get, update, and remove subscription topics.
- **Contact Properties** — Create, list, get, update, and remove custom contact attributes.
- **API Keys** — Create, list, and remove API keys.
- **Webhooks** — Create, list, get, update, and remove webhooks for event notifications.
- **Templates** — Create, list, get, update, and remove email templates.
## Prerequisites
You'll need a supported MCP client and `npx` installed on your machine.
- [Create an API key](https://app.reloop.sh/api-keys)
- [Verify your domain](https://app.reloop.sh/domains)
## How to use the MCP Server
Replace `rl_xxxxxxxxx` with your actual Reloop API key.
### Stdio Transport (Default)
```bash
claude mcp add reloop -e RELOOP_API_KEY=rl_xxxxxxxxx -- npx -y reloop-mcp
```
```bash
codex mcp add reloop \
--env RELOOP_API_KEY=rl_xxxxxxxxx \
-- npx -y reloop-mcp
```
```json
{
"mcpServers": {
"reloop": {
"command": "npx",
"args": ["-y", "reloop-mcp"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
```json
{
"mcpServers": {
"reloop": {
"command": "npx",
"args": ["-y", "reloop-mcp"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
Add the following to your VS Code `settings.json`:
```json
{
"mcp": {
"servers": {
"reloop": {
"command": "npx",
"args": ["-y", "reloop-mcp"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
}
```
```json
{
"mcpServers": {
"reloop": {
"command": "npx",
"args": ["-y", "reloop-mcp"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
Add to your `opencode.json`:
```json
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"reloop": {
"type": "local",
"command": ["npx", "-y", "reloop-mcp"],
"enabled": true,
"environment": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
```json
{
"mcpServers": {
"reloop": {
"command": "npx",
"args": ["-y", "reloop-mcp"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
### HTTP Transport
For HTTP transport, the API key is passed via the `Authorization` header instead of an environment variable.
Start the server:
```bash
npx -y reloop-mcp --http --port 3000
```
The server will be available at `http://127.0.0.1:3000` with the MCP endpoint at `/mcp`.
```bash
claude mcp add reloop --transport http http://127.0.0.1:3000/mcp --header "Authorization: Bearer rl_xxxxxxxxx"
```
```json
{
"mcpServers": {
"reloop": {
"url": "http://127.0.0.1:3000/mcp",
"headers": {
"Authorization": "Bearer rl_xxxxxxxxx"
}
}
}
}
```
You can customize the port with the `MCP_PORT` environment variable:
```bash
MCP_PORT=3000 npx -y reloop-mcp --http
```
### Options
**CLI flags:**
- `--key`: Your Reloop API key (stdio mode only; HTTP mode uses the Bearer token from the client)
- `--sender`: Default sender email address from a verified domain
- `--reply-to`: Default reply-to email address (can be specified multiple times)
- `--http`: Use HTTP transport instead of stdio (default: stdio)
- `--port`: HTTP port when using `--http` (default: 3000, or `MCP_PORT` env var)
**Environment variables:**
- `RELOOP_API_KEY`: Your Reloop API key (required for stdio, optional for HTTP)
- `SENDER_EMAIL_ADDRESS`: Default sender email address from a verified domain (optional)
- `REPLY_TO_EMAIL_ADDRESSES`: Comma-separated reply-to email addresses (optional)
- `MCP_PORT`: HTTP port when using `--http` (optional)
## Local Development
```bash
git clone https://github.com/reloop-labs/reloop-mcp.git
pnpm install
pnpm run build
```
Replace `npx` commands above with direct `node` commands.
### Stdio
```bash
claude mcp add reloop -e RELOOP_API_KEY=rl_xxxxxxxxx -- node ABSOLUTE_PATH_TO_PROJECT/dist/index.js
```
```bash
codex mcp add reloop \
--env RELOOP_API_KEY=rl_xxxxxxxxx \
-- node ABSOLUTE_PATH_TO_PROJECT/dist/index.js
```
```json
{
"mcpServers": {
"reloop": {
"command": "node",
"args": ["ABSOLUTE_PATH_TO_PROJECT/dist/index.js"],
"env": {
"RELOOP_API_KEY": "rl_xxxxxxxxx"
}
}
}
}
```
### HTTP
```bash
node ABSOLUTE_PATH_TO_PROJECT/dist/index.js --http --port 3000
```
```bash
claude mcp add reloop --transport http http://127.0.0.1:3000/mcp --header "Authorization: Bearer rl_xxxxxxxxx"
```
```json
{
"mcpServers": {
"reloop": {
"url": "http://127.0.0.1:3000/mcp",
"headers": {
"Authorization": "Bearer rl_xxxxxxxxx"
}
}
}
}
```
## Testing with MCP Inspector
Follow the [Local Development](#local-development) steps above first.
### Using Stdio Transport
1. Set your API key:
```bash
export RELOOP_API_KEY=rl_your_key_here
```
2. Start the inspector:
```bash
pnpm inspector
```
3. Configure in the browser:
- Choose **stdio** (launch a process)
- Command: `node`
- Args: `dist/index.js` (or the full path to `dist/index.js`)
- Env: `RELOOP_API_KEY=rl_your_key_here`
- Click **Connect**, then use "List tools" to verify the server is working
### Using HTTP Transport
1. Start the HTTP server:
```bash
node dist/index.js --http --port 3000
```
2. Start the inspector:
```bash
pnpm inspector
```
3. Configure in the browser:
- Choose **Streamable HTTP** (connect to URL)
- URL: `http://127.0.0.1:3000/mcp`
- Add a custom header: `Authorization: Bearer rl_your_key_here` and activate the toggle
- Click **Connect**, then use "List tools" to verify the server is working