RelayRailRelayRail
Documentation

Introduction

RelayRail is the human-in-the-loop primitive for AI agents. Give your agents a phone number with a single MCP server.

What is RelayRail?

RelayRail enables your AI agents to communicate with you via SMS and email. When your agent needs approval, wants to notify you of something important, or needs human input, it reaches out through RelayRail. You respond from your phone - no laptop required.

Key Features

MCP Native

Works with Claude Desktop, Cursor, Cline, and any MCP-compatible agent. No SDK required.

Multi-Channel

SMS and email notifications with intelligent routing based on urgency and preferences.

Multi-Agent Support

Each agent gets its own dedicated phone number. Manage multiple agents from one account.

Enterprise Ready

A2P 10DLC compliant SMS, audit trails, and SOC2-ready infrastructure.

Quick Start

Terminal
# Install and start the MCP server
npx @relayrail/server start

# Or add to your MCP config
{
  "mcpServers": {
    "relayrail": {
      "command": "npx",
      "args": ["@relayrail/server", "start"],
      "env": {
        "RELAYRAIL_API_KEY": "your-api-key"
      }
    }
  }
}

How It Works

  1. Sign up for a RelayRail account and create an agent
  2. Configure the MCP server in your AI tool (Claude, Cursor, etc.)
  3. Your agent calls request_approval when it needs human input
  4. You receive an SMS or email with the request
  5. You reply from your phone - the agent continues
Get StartedAPI Reference