Voice Call MCP Server

What is Voice Call MCP Server?

Voice Call MCP Server is a Model Context Protocol (MCP) server that enables AI assistants like Claude to initiate and manage outbound phone calls using Twilio and the OpenAI GPT-4o Realtime model. It is designed for developers who want to build AI-powered voice calling applications.

How to use Voice Call MCP Server?

Clone the repository, install dependencies (npm install && npm run build), set required environment variables (Twilio credentials, OpenAI API key, ngrok authtoken), and configure Claude Desktop to use the server by adding it to the MCP servers config. After restarting Claude Desktop, you can ask Claude to make voice calls using natural language commands.

Key features of Voice Call MCP Server

• 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 (e.g., restaurant reservations)
• Automatic public URL tunneling with ngrok
• Secure handling of credentials

Use cases of Voice Call MCP Server

• Notify someone you’ll be late for a meeting via a phone call
• Make restaurant reservations and specify language preferences
• Reschedule appointments by calling a business and speaking with a receptionist

FAQ from Voice Call MCP Server

What phone number format is required?

All phone numbers must be in E.164 format (e.g., +11234567890).

What are the runtime dependencies?

Node.js >= 22, a Twilio account with API credentials, an OpenAI API key, and an ngrok authtoken are required.

Where does the call audio flow?

Audio is forwarded from Twilio to OpenAI’s realtime model and then streamed back to the destination phone through Twilio. An ngrok tunnel exposes your server publicly for Twilio webhooks.

Are there any rate limits or costs to be aware of?

Yes, be aware of your Twilio and OpenAI account’s rate limits and pricing. Call durations affect costs for both services.

How is the server secured?

Credentials are stored in environment variables. The ngrok tunnel uses a random URL protected by a random secret, but public exposure should still be considered.