AI-Powered Voice Call & SMS MCP Server
A Model Context Protocol (MCP) server that enables Claude and other AI assistants to initiate and manage voice calls and SMS messages using Twilio and OpenAI (GPT-4o Realtime model).
Use this as a base to kick-start your AI-powered voice calling and messaging 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) 🍽️
- Public URL support via nginx reverse proxy 🔄
- 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 using
nvm(Node Version Manager):nvm install 22 nvm use 22
- If you need to update Node.js, we recommend using
- Twilio account with API credentials
- OpenAI API key
- Public URL with nginx reverse proxy (or similar) for Twilio webhooks
-
Clone the repository
git clone https://github.com/sackio/phony.git cd phony -
Install dependencies and build
npm install npm run build
The server requires several environment variables. Copy .env.example to .env and configure:
cp .env.example .envPUBLIC_URL: Your public URL for Twilio callbacks (e.g.,https://your-domain.com)TWILIO_ACCOUNT_SID: Your Twilio account SIDTWILIO_AUTH_TOKEN: Your Twilio auth tokenTWILIO_NUMBER: Your Twilio number (in E.164 format)OPENAI_API_KEY: Your OpenAI API key
MongoDB is configured with authentication enabled. Generate a secure password:
openssl rand -base64 32Then configure in .env:
MONGODB_USERNAME: Database username (default:voicecalls_admin)MONGODB_PASSWORD: Randomly generated password (use command above)MONGODB_DATABASE: Database name (default:phony)MONGODB_URI: Full connection string with authentication
.env to version control. The .env.example file contains placeholder values only.
RECORD_CALLS: Set to "true" to record calls (optional)PORT: Server port (optional, defaults to 3004)API_SECRET: Webhook security secret (randomly generated if not set)
You need to configure nginx (or similar reverse proxy) to forward requests to the server. Example nginx location block:
# Phony - Twilio webhooks and WebSocket
location /call/ {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_read_timeout 600s;
proxy_connect_timeout 600s;
proxy_send_timeout 600s;
proxy_pass http://localhost:3004;
}Note: The /call/ location should not require authentication as Twilio needs to access these endpoints.
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": {
"phony": {
"command": "node",
"args": ["/path/to/your/phony/dist/start-all.cjs"],
"env": {
"PUBLIC_URL": "https://your-domain.com",
"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"
}
}
}
}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:
- Simple call:
Can you call +1-123-456-7890 and let them know I'll be 15 minutes late for our meeting?
- Restaurant reservation:
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.
- Appointment scheduling:
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: Ensure your nginx configuration properly secures endpoints while allowing Twilio webhook access to
/call/routes
Common error messages and solutions:
-
"Phone number must be in E.164 format"
- Make sure the phone number starts with "+" and the country code
-
"Invalid credentials"
- Double-check your TWILIO_ACCOUNT_SID and TWILIO_AUTH_TOKEN. You can copy them from the Twilio Console
-
"OpenAI API error"
- Verify your OPENAI_API_KEY is correct and has sufficient credits
-
"PUBLIC_URL environment variable is required"
- Make sure you've set the PUBLIC_URL environment variable to your public domain (e.g.,
https://your-domain.com) - Ensure your nginx reverse proxy is properly configured to forward
/call/requests to the server
- Make sure you've set the PUBLIC_URL environment variable to your public domain (e.g.,
-
"OpenAI Realtime does not detect the end of voice input, or is lagging."
- Sometimes, there might be voice encoding issues between Twilio and the receiver's network operator. Try using a different receiver.
Contributions are welcome! Here are some areas we're looking to improve:
- Implement support for multiple AI models beyond the current implementation
- Add database integration to store conversation history locally and make it accessible for AI context
- Improve latency and response times to enhance call experiences
- Enhance error handling and recovery mechanisms
- Add more pre-built conversation templates for common scenarios
- Implement improved call monitoring and analytics
If you'd like to contribute, please open an issue to discuss your ideas before submitting a pull request.
Phony is a fork of the Voice Call MCP Server originally created by the Popcorn team.
We've extended it with:
- SMS messaging capabilities (send, receive, conversation tracking)
- Incoming call handling with proper greeting protocols
- Human-in-the-loop call management with real-time context injection
- React frontend UI for call and SMS management
- Call hold/resume functionality with TTS hold messages
- Enhanced features and comprehensive documentation
This project is licensed under the MIT License - see the LICENSE file for details.
Please do not include any sensitive information (like phone numbers or API credentials) in GitHub issues or pull requests. This server handles sensitive communications; deploy it responsibly and ensure all credentials are kept secure.