ElevenLabs MCP Backend

Production-grade backend service that connects ElevenLabs Agents to Supabase using MCP (Model Context Protocol). Enables voice agents to look up real-time order details via the lookup_order tool.

Features

• ✅ MCP Server (Streamable HTTP) - Full JSON-RPC 2.0 implementation
• ✅ Supabase Integration - Real-time order data queries
• ✅ Bearer Token Authentication - Secure API access
• ✅ Health Check Endpoint - Service monitoring
• ✅ REST Backup Endpoint - Alternative to MCP for testing
• ✅ Structured Logging - Request tracking and error handling
• ✅ Production Ready - Works on Replit, Railway, Render, Fly, Vercel

Architecture

ElevenLabs Agent → MCP Server (/mcp) → Supabase → Orders Table

The MCP server implements the following JSON-RPC 2.0 methods:

• initialize - Protocol handshake
• ping - Health check
• tools/list - List available tools
• tools/call - Execute tools (lookup_order)

Quick Start

Prerequisites

• Node.js 18+
• Supabase account and project
• ElevenLabs account with Agents feature

1. Clone and Install

git clone <your-repo>
cd elevenlabs-mcp-backend
npm install

2. Set Up Supabase

1. Go to your Supabase project dashboard
2. Open the SQL Editor
3. Run the SQL from sql/schema.sql to create the orders table and seed data

3. Configure Environment Variables

Copy env.example to .env:

cp env.example .env

Edit .env with your values:

PORT=3000
MCP_SECRET=your-secure-random-string-here
SUPABASE_URL=https://your-project.supabase.co
SUPABASE_SERVICE_ROLE_KEY=your-service-role-key

Generate a secure MCP_SECRET:

openssl rand -hex 32

Get Supabase credentials:

• SUPABASE_URL: Found in Project Settings → API → Project URL
• SUPABASE_SERVICE_ROLE_KEY: Found in Project Settings → API → service_role key (⚠️ Keep secret!)

4. Build and Run

Development:

npm run dev

Production:

npm run build
npm start

The server will start on http://localhost:3000 (or your PORT env var).

Testing

Health Check

curl http://localhost:3000/health

Expected response:

{
  "ok": true,
  "service": "elevenlabs-mcp-backend",
  "timestamp": "2025-12-23T12:00:00.000Z"
}

MCP: tools/list

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer your-secure-random-string-here" \
  -d '{
    "jsonrpc": "2.0",
    "id": "1",
    "method": "tools/list",
    "params": {}
  }'

Expected response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "tools": [
      {
        "name": "lookup_order",
        "description": "Looks up order details by order ID...",
        "inputSchema": {
          "type": "object",
          "properties": {
            "order_id": {
              "type": "string",
              "description": "The order ID to look up (e.g., 'TR-10001')"
            }
          },
          "required": ["order_id"]
        }
      }
    ]
  }
}

MCP: tools/call (Existing Order)

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer your-secure-random-string-here" \
  -d '{
    "jsonrpc": "2.0",
    "id": "2",
    "method": "tools/call",
    "params": {
      "name": "lookup_order",
      "arguments": {
        "order_id": "TR-10001"
      }
    }
  }'

Expected response:

{
  "jsonrpc": "2.0",
  "id": "2",
  "result": {
    "content": [
      {
        "type": "text",
        "text": "Order TR-10001 is SHIPPED. ETA: December 28, 2025. Tracking: 123456789 (Yurtiçi Kargo). Last updated: December 23, 2025, 10:30 AM."
      }
    ],
    "structured": {
      "order_id": "TR-10001",
      "status": "SHIPPED",
      "eta": "2025-12-28",
      "carrier": "Yurtiçi Kargo",
      "tracking_number": "123456789",
      "last_update": "2025-12-23T10:30:00Z"
    }
  }
}

MCP: tools/call (Missing Order)

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer your-secure-random-string-here" \
  -d '{
    "jsonrpc": "2.0",
    "id": "3",
    "method": "tools/call",
    "params": {
      "name": "lookup_order",
      "arguments": {
        "order_id": "TR-99999"
      }
    }
  }'

Expected response:

{
  "jsonrpc": "2.0",
  "id": "3",
  "error": {
    "code": -32004,
    "message": "Order not found: TR-99999"
  }
}

REST Backup Endpoint

curl -X POST http://localhost:3000/lookup-order \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer your-secure-random-string-here" \
  -d '{
    "order_id": "TR-10001"
  }'

Expected response:

{
  "order_id": "TR-10001",
  "status": "SHIPPED",
  "eta": "2025-12-28",
  "carrier": "Yurtiçi Kargo",
  "tracking_number": "123456789",
  "last_update": "2025-12-23T10:30:00Z",
  "issue_flag": null,
  "notes": "Out for delivery",
  "formatted_text": "Order TR-10001 is SHIPPED. ETA: December 28, 2025. Tracking: 123456789 (Yurtiçi Kargo). Last updated: December 23, 2025, 10:30 AM."
}

ElevenLabs Configuration

Setting Up MCP Server in ElevenLabs

1. Deploy your backend to a public URL (e.g., https://your-app.railway.app or https://your-app.vercel.app)

2. In ElevenLabs Dashboard:

   • Go to Agents → Select your agent → Tools → MCP Servers
   • Click Add MCP Server

3. Configure the MCP Server:

   • MCP Server URL: https://your-domain.com/mcp
   • Header: Authorization: Bearer <your-MCP_SECRET>
   • Tool Approval Mode:
     • Always Ask (recommended for production)
     • No Approval (for testing/demo)

4. Test Connection:

   • Click Test Connection in ElevenLabs
   • Should see: ✅ Connection successful
   • The lookup_order tool should appear in available tools

Important Security Notes

⚠️ Only agents with this MCP server attached can use the tool.

• Not "all agents can read the DB"
• Only agents that have this MCP server connected and permission
• Each agent must have the MCP server configured individually

Agent System Prompt Fix

If your agent prompt currently says:

"You have access only to uploaded TXT order records"

Replace it with:

"You have access to real-time order records using the lookup_order tool. When a user asks about an order, always call the lookup_order tool with the order_id. Never guess order details - always use the tool to retrieve accurate information."

Keep these guardrails:

• Never guess order details
• Always call the lookup_order tool when asked about orders
• If the tool returns "Order not found", inform the user clearly

Deployment

Railway

1. Connect your GitHub repo to Railway
2. Railway auto-detects Node.js
3. Add environment variables in Railway dashboard:
   • PORT (auto-set by Railway, but can override)
   • MCP_SECRET
   • SUPABASE_URL
   • SUPABASE_SERVICE_ROLE_KEY
4. Deploy!

Render

1. Create new Web Service
2. Connect your repo
3. Build command: npm install && npm run build
4. Start command: npm start
5. Add environment variables
6. Deploy!

Vercel

1. Install Vercel CLI: npm i -g vercel
2. Run vercel in project directory
3. Add environment variables in Vercel dashboard
4. Note: Vercel serverless may have cold starts. Consider Railway/Render for better MCP performance.

Fly.io

1. Install Fly CLI
2. Run fly launch
3. Add secrets: fly secrets set MCP_SECRET=... SUPABASE_URL=... SUPABASE_SERVICE_ROLE_KEY=...
4. Deploy: fly deploy

Replit

1. Import your GitHub repo
2. Add environment variables in Secrets tab
3. Run npm install && npm run build && npm start
4. Replit auto-exposes the port

API Reference

Endpoints

GET /health

Health check (no auth required)

Response:

{
  "ok": true,
  "service": "elevenlabs-mcp-backend",
  "timestamp": "2025-12-23T12:00:00.000Z"
}

POST /mcp

MCP JSON-RPC 2.0 endpoint (requires Bearer token)

Headers:

• Authorization: Bearer <MCP_SECRET>
• Content-Type: application/json

Request Body: JSON-RPC 2.0 format

{
  "jsonrpc": "2.0",
  "id": "1",
  "method": "tools/call",
  "params": { ... }
}

Response: JSON-RPC 2.0 format

POST /lookup-order

REST backup endpoint (requires Bearer token)

Headers:

• Authorization: Bearer <MCP_SECRET>
• Content-Type: application/json

Request Body:

{
  "order_id": "TR-10001"
}

Response:

{
  "order_id": "TR-10001",
  "status": "SHIPPED",
  "eta": "2025-12-28",
  "carrier": "Yurtiçi Kargo",
  "tracking_number": "123456789",
  "last_update": "2025-12-23T10:30:00Z",
  "issue_flag": null,
  "notes": "Out for delivery",
  "formatted_text": "..."
}

Error Codes

JSON-RPC 2.0 error codes:

• -32700: Parse error
• -32600: Invalid request
• -32601: Method not found
• -32602: Invalid params
• -32603: Internal error
• -32004: Order not found (custom)

Database Schema

The orders table has the following structure:

CREATE TABLE orders (
  id UUID PRIMARY KEY,
  order_id TEXT UNIQUE NOT NULL,
  status TEXT NOT NULL, -- PROCESSING, SHIPPED, DELIVERED, CANCELED, RETURNED, ON_HOLD
  eta DATE,
  carrier TEXT,
  tracking_number TEXT,
  last_update TIMESTAMPTZ DEFAULT NOW(),
  issue_flag TEXT, -- e.g., "address_problem", "payment_review"
  notes TEXT,
  created_at TIMESTAMPTZ DEFAULT NOW(),
  updated_at TIMESTAMPTZ DEFAULT NOW()
);

See sql/schema.sql for full schema and seed data.

Development

Project Structure

.
├── src/
│   ├── server.ts      # Fastify server and routes
│   ├── mcp.ts         # MCP JSON-RPC handler
│   ├── supabase.ts    # Supabase client and queries
│   ├── auth.ts        # Bearer token middleware
│   ├── logger.ts      # Structured logging
│   └── types.ts       # TypeScript types
├── sql/
│   └── schema.sql     # Database schema and seeds
├── dist/              # Compiled JavaScript (generated)
├── package.json
├── tsconfig.json
├── env.example
└── README.md

Scripts

• npm run dev - Development with hot reload (tsx watch)
• npm run build - Compile TypeScript to JavaScript
• npm start - Run production server
• npm run type-check - Type check without building

Logging

Logs include:

• Request IDs for tracing
• Method names (MCP methods)
• Tool names
• Order IDs
• Errors (safely, no secrets exposed)

Example log:

[2025-12-23T12:00:00.000Z] [INFO] Processing MCP request {"requestId":"123-abc","method":"tools/call","id":"2"}
[2025-12-23T12:00:00.100Z] [INFO] Order found {"requestId":"123-abc","orderId":"TR-10001","status":"SHIPPED"}

Troubleshooting

"Order not found" for valid orders

• Check Supabase connection: Verify SUPABASE_URL and SUPABASE_SERVICE_ROLE_KEY
• Check table exists: Run sql/schema.sql in Supabase SQL Editor
• Check order_id format: Must match exactly (case-sensitive)

MCP "Test Connection" fails in ElevenLabs

• Verify server is deployed and accessible
• Check Authorization header format: Bearer <token> (with space)
• Verify MCP_SECRET matches in both places
• Check server logs for authentication errors

CORS errors

• Server allows all origins by default (origin: true)
• For production, restrict in src/server.ts CORS config

Supabase connection errors

• Service role key must have full access (bypasses RLS)
• Verify URL format: https://xxxxx.supabase.co (no trailing slash)
• Check network/firewall allows outbound HTTPS

Final Checklist

After deployment, verify:

• ✅ Server running
• ✅ /health works
• ✅ /mcp tools/list works
• ✅ /mcp tools/call works
• ✅ Supabase returns rows
• ✅ ElevenLabs "Test Connection" passes
• ✅ Voice agent can answer "Where is my order TR-10001?"

License

MIT

Support

For issues or questions:

1. Check server logs for detailed error messages
2. Verify environment variables are set correctly
3. Test with curl commands above
4. Check Supabase dashboard for data

Built with: Fastify, TypeScript, Supabase, MCP (Model Context Protocol)