Managed Agents at Previously $0.06 $0.03/minManaged Agents are Previously $0.06 $0.03/min.
Official

Twilio AI voice agents on the phone numbers you already own

Link a Twilio account once, import the numbers you want and assign an agent, with calls at your Twilio rates, international numbers included.

Start buildingRead the docs
link-twilio.sh
curl -X POST "https://api.cartesia.ai/agents/phone-numbers/providers" \
  -H "X-API-Key: $CARTESIA_API_KEY" \
  -H "Cartesia-Version: 2026-08-14" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "twilio",
    "account_sid": "YOUR_TWILIO_ACCOUNT_SID",
    "api_key_sid": "YOUR_API_KEY_SID",
    "api_key_secret": "YOUR_API_KEY_SECRET",
    "region": "us1"
  }'

What a Twilio AI voice agent can do

What teams build when they put Cartesia and Twilio together.

Keep your numbers

Numbers you already own stay in your Twilio account. Cartesia routes their calls to the agent you assign to each one.

International numbers

Import international numbers from your Twilio account too. The agent can call international numbers at your Twilio rates.

Regional routing

Pick us1, ie1 or au1 when you link the account to choose which Twilio region handles the calls. Each non-default region needs its own API key.

More code for Twilio

Cartesia checks the credentials against Twilio before saving them.

Cartesia docs: Twilio integration
import-number.sh
curl -X POST "https://api.cartesia.ai/agents/phone-numbers" \
  -H "X-API-Key: $CARTESIA_API_KEY" \
  -H "Cartesia-Version: 2026-08-14" \
  -H "Content-Type: application/json" \
  -d '{
    "label": "Support line",
    "number": "+14155551234",
    "provider": { "id": "YOUR_PROVIDER_ID" }
  }'

Set it up

Documented by Cartesia: you link a Twilio account with an API key and import numbers. Cartesia validates the credentials with Twilio before it saves them. Vendor details read in October 2026.

  1. Create a subaccount (recommended)

    A dedicated Twilio subaccount keeps the numbers and credentials you share with Cartesia apart from the rest.

  2. Create a Standard API key

    Save the SID and secret. Twilio shows the secret once. Use one key per region.

  3. Link the account

    In the Playground, open Phone Numbers, select Add Number, then Import from Twilio. Or call the API.

  4. Import a number and assign an agent

    The number must already exist in Twilio. Cartesia does not buy numbers for you.

Documentation

Before you build

Rotate keys without downtime

Create a new key, update the provider in Cartesia, then revoke the old one. Cartesia verifies each assigned number before it saves.

Elastic SIP Trunking is a different route

If you use Twilio's SIP trunks rather than numbers, follow the SIP trunking page. Twilio does not support digest authentication for inbound origination, so use allowed addresses.

Use cases for teams on Twilio

Customer support

Resolve support calls on the first try, refund and credit within your rules, and keep customers who call to cancel.

See the use case

Appointment scheduling

Book, reschedule and confirm appointments on your calendar, 24/7.

See the use case

More integrations

All integrations
Guide

Bandwidth

Stream Bandwidth calls to Cartesia speech to text and text to speech over WebSockets, with no audio resampling.

  • Sonic
  • Ink
See the integration
SIP trunk

Telnyx

Run a Cartesia voice agent on Telnyx numbers with a SIP trunk, at your Telnyx rates.

  • Managed Agents
See the integration
SIP trunk

Plivo

Run a Cartesia voice agent on Plivo numbers with a Zentrunk SIP trunk, at your Plivo rates.

  • Managed Agents
See the integration

Enterprise-grade security

  • HIPAA compliant badge

    HIPAA compliant

  • SOC 2 Type 2 badge

    SOC 2 Type 2

  • GDPR badge

    GDPR

Twilio AI voice agent FAQs

How do I connect Twilio to an AI voice agent?

Link your Twilio account to Cartesia with a Standard API key, import the numbers you want and assign an agent to each. In the Playground that is Phone Numbers, Add Number, Import from Twilio, or one API call per step. Cartesia checks the key with Twilio before it saves it. A dedicated Twilio subaccount keeps the shared numbers apart from the rest of your account.

Does Twilio have its own AI voice agent?

Twilio sells ConversationRelay, which turns call audio into text and sends it over a WebSocket to an LLM app that you build and host. With Cartesia, the agent itself runs on Cartesia, including speech, tools and transfers, and Twilio only carries the call on your number.

Does Cartesia buy Twilio numbers for me?

No. The number has to exist in your Twilio account before you import it, and Cartesia never buys numbers there. If you don't want a Twilio account at all, Cartesia can provision US numbers itself, with a telephony fee of $0.014 per minute.

Who bills the minutes on a Twilio number?

Both, for different things. Agents run at $0.03/min, plus LLM usage and telephony, and on a linked Twilio number the telephony is Twilio's own bill at your Twilio rates. Cartesia's telephony fee applies only to numbers Cartesia provisions. The Twilio pricing guide breaks down what Twilio charges per minute.

Can the agent transfer a Twilio call to a person?

Yes. Add a transfer_to_number system tool with the destination number and a condition such as "The caller asks for a person", and the agent makes a cold transfer. Transfers work on Twilio and SIP trunk numbers, so a linked Twilio number can transfer.

Can I use Twilio Elastic SIP Trunking instead?

Yes, but it is a separate setup. Follow the SIP trunking page and use allowed addresses for inbound calls, because Twilio does not support digest authentication for inbound origination. Linking numbers with an API key, as on this page, needs no trunk.

Get started today

Talk to an expert.

Connect with a member of our team and learn how Cartesia can help you build world-class voice experiences.

Contact Sales

Start building.

Access our models via API and bring a voice agent into production in minutes.

Try Cartesia