This is the full example of the Inbound Call Quickstart.

This guide walks you through connecting inbound phone calls using Twilio to an Ultravox agent.

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Prerequisites

  • Node.js 20 or higher
  • A Twilio account with:
    • Account SID
    • Auth Token
    • Phone Number
  • An Ultravox API key
  • For incoming calls: A publicly accessible URL for your webhook (e.g., using ngrok)

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Set-up and Installation

1

Get the Source Code

Copy all the code locally from the twilio-inbound-quickstart-js example.

2

Install the Required Dependencies

pnpm install

or

npm install

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Configure Twilio Webhook

1

Make Your Server Publicly Accessible

Use ngrok or a similar service to create a public URL for your local server:

ngrok http 3000
2

Set Up Webhook

  1. Go to your Twilio Console
  2. Navigate to your phone number’s configuration
  3. Under “Voice & Fax”, set the webhook URL for incoming calls to: https://your-ngrok-url/incoming

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Update Configuration

The AI assistant will introduce itself as Steve and have a conversation with the recipient. You need to update the variable for the Ultravox API key. You may also (optionally) update the system prompt.

  • ULTRAVOX_API_KEY: Your Ultravox API key
  • SYSTEM_PROMPT: Instructions for the AI agent’s behavior
Configuring Variables
// Ultravox configuration
const ULTRAVOX_API_KEY = 'your_ultravox_api_key_here';
const SYSTEM_PROMPT = 'Your name is Steve. You are receiving a phone call. Ask them their name and see how they are doing.';

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Start the Server

Run the server:

pnpm start

or

npm start

Now, when someone calls your Twilio number, they’ll be connected to your AI assistant.

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Next Steps

  1. Check out the Outbound Phone Call example.
  2. Ultravox Realtime provides telephony integrations for Telnyx, Twilio, Plivo, and Exotel. Learn more here.

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Additional Resources