Voice Call MCP Server

A Model Context Protocol (MCP) server that enables Claude and other AI assistants to initiate and manage voice calls using Twilio and OpenAI (GPT-4o Realtime model).

Use this as a base to kick-start your AI-powered voice calling explorations, save time and develop additional functionality on top of it.

sequenceDiagram participant AI as AI Assistant (e.g., Claude) participant MCP as MCP Server participant Twilio as Twilio participant Phone as Destination Phone participant OpenAI as OpenAI AI->>MCP: 1) Initiate outbound call request <br>(POST /calls) MCP->>Twilio: 2) Place outbound call via Twilio API Twilio->>Phone: 3) Ring the destination phone Twilio->>MCP: 4) Call status updates & audio callbacks (webhooks) MCP->>OpenAI: 5) Forward real-time audio to OpenaAI's realtime model OpenAI->>MCP: 6) Return voice stream MCP->>Twilio: 7) Send voice stream Twilio->>Phone: 8) Forward voice stream Note over Phone: Two-way conversation continues <br>until the call ends

- Make outbound phone calls via Twilio 📞
- Process call audio in real-time with GPT-4o Realtime model 🎙️
- Real-time language switching during calls 🌐
- Pre-built prompts for common calling scenarios (like restaurant reservations) 🍽️
- Automatic public URL tunneling with ngrok 🔄
- Secure handling of credentials 🔒

The Model Context Protocol (MCP) bridges the gap between AI assistants and real-world actions. By implementing MCP, this server allows AI models like Claude to:
- Initiate actual phone calls on behalf of users
- Process and respond to real-time audio conversations
- Execute complex tasks requiring voice communication

This open-source implementation provides transparency and customizability, allowing developers to extend functionality while maintaining control over their data and privacy.

- Node.js >= 22

- If you need to update Node.js, we recommend usingnvm(Node Version Manager):

nvm install 22 nvm use 22

git clone https://github.com/lukaskai/voice-call-mcp-server.git cd voice-call-mcp-server

The server requires several environment variables:

- TWILIO_ACCOUNT_SID: Your Twilio account SID
- TWILIO_AUTH_TOKEN: Your Twilio auth token
- TWILIO_NUMBER: Your Twilio number
- OPENAI_API_KEY: Your OpenAI API key
- NGROK_AUTHTOKEN: Your ngrok authtoken
- RECORD_CALLS: Set to "true" to record calls (optional)

To use this server with Claude Desktop, add the following to your configuration file:

macOS:~/Library/Application Support/Claude/claude_desktop_config.json

Windows:%APPDATA%\Claude\claude_desktop_config.json

{ "mcpServers": { "voice-call": { "command": "node", "args": ["/path/to/your/mcp-new/dist/start-all.cjs"], "env": { "TWILIO_ACCOUNT_SID": "your_account_sid", "TWILIO_AUTH_TOKEN": "your_auth_token", "TWILIO_NUMBER": "your_e.164_format_number", "OPENAI_API_KEY": "your_openai_api_key", "NGROK_AUTHTOKEN": "your_ngrok_authtoken" } } } }

After that, restart Claude Desktop to reload the configuration. If connected, you should see Voice Call under the 🔨 menu.

Here are some natural ways to interact with the server through Claude:

Can you call +1-123-456-7890 and let them know I'll be 15 minutes late for our meeting?

Please call Delicious Restaurant at +1-123-456-7890 and make a reservation for 4 people tonight at 7:30 PM. Please speak in German.

Please call Expert Dental NYC (+1-123-456-7899) and reschedule my Monday appointment to next Friday between 4–6pm.

- Phone Number Format: All phone numbers must be in E.164 format (e.g., +11234567890)
- Rate Limits: Be aware of your Twilio and OpenAI account's rate limits and pricing
- Voice Conversations: The AI will handle natural conversations in real-time
- Call Duration: Be mindful of call durations as they affect OpenAI API and Twilio costs
- Public Exposure: Be aware that the ngrok tunnel exposes your server publicly for Twilio to reach it (though with a random URL and protected by a random secret)
-

"Phone number must be in E.164 format"

- Make sure the phone number starts with "+" and the country code

- Double-check your TWILIO_ACCOUNT_SID and TWILIO_AUTH_TOKEN. You can copy them from theTwilio Console

Curious? Head tocareers.popcorn.space🍿 !

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Interact with the Didlogic API for telecommunication services, including virtual phone numbers and SMS.