Phone Numbers - Cartesia Docs

Cartesia supports three ways to connect phone numbers to your agents: Cartesia-provisioned numbers, numbers imported from Twilio, and numbers connected through your SIP carrier. Agent calling rates apply to all three options. Cartesia charges an additional telephony fee only when you use a Cartesia-provisioned number.

Feature	Cartesia Numbers	Twilio Numbers	SIP Trunk Numbers
Number origin	US only	Any country available in Twilio	Any country available from your carrier
Inbound calls	✓	✓	✓ with inbound configured
Outbound to US	✓	✓	✓ with outbound configured
Outbound international	✗	✓ at your Twilio cost	Carrier-dependent, with outbound configured
Regional routing	N/A	Configurable	Carrier-dependent
Provisioning	Automatic	Import from Twilio	Import from your carrier
Telephony cost	+$0.014/min add-on	Your Twilio rates apply	Your carrier rates apply

Cartesia Numbers

Cartesia provisions US phone numbers tied to your subscription plan. Provision numbers from the Playground or via the API and assign them to agents immediately. See the Cartesia Numbers guide for setup and management.

Twilio Numbers (Bring Your Own)

Import phone numbers from your Twilio account for full international support, including inbound and outbound calling to any destination supported by Twilio. See the Twilio Integration guide for step-by-step setup.

SIP Trunk Numbers (Bring Your Own Carrier)

Connect an existing SIP trunk for inbound and outbound calls through your carrier. You configure access controls, signaling transport, media encryption, and outbound authentication when you register the trunk. See the SIP Trunking guide for setup instructions.

Managing Numbers

View and manage Cartesia, Twilio, and SIP trunk numbers in the Phone Numbers dashboard, through the Phone Numbers API, or with the CLI.

Phone Numbers tab listing numbers in the Playground — Phone Numbers in the Playground

List all phone numbers from the CLI:

cartesia phone-numbers ls

Filter by provider type or agent:

cartesia phone-numbers ls --type twilio
cartesia phone-numbers ls --type sip_trunk
cartesia phone-numbers ls --agent-id <agent-id>

Assigning an Inbound Agent

Assigning a phone number to an agent routes inbound calls on that number to the agent. A number can only be assigned to one agent at a time, but an agent can have multiple numbers route to it.

Playground
CLI
API

Click on a phone number to open its detail page
In the Agent card, search for and select your agent

cartesia phone-numbers assign <phone-number-id> --agent-id <agent-id>

To unassign a number from its agent:

cartesia phone-numbers unassign <phone-number-id>

curl -X PATCH "https://api.cartesia.ai/agents/phone-numbers/YOUR_PHONE_NUMBER_ID" \
  -H "Authorization: Bearer $CARTESIA_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Cartesia-Version: 2026-03-01" \
  -d '{
    "agent_id": "YOUR_AGENT_ID"
  }'

To unassign, set agent_id to null.

Outbound-only numbers

Import or provision a number, and then pass its ID as from_number_id when placing outbound calls.

curl -X POST "https://api.cartesia.ai/agents/calls" \
  -H "X-API-Key: $CARTESIA_API_KEY" \
  -H "Cartesia-Version: 2026-03-01" \
  -H "Content-Type: application/json" \
  -d '{
    "from_number_id": "YOUR_PHONE_NUMBER_ID",
    "agent_id": "YOUR_AGENT_ID",
    "outbound_calls": [{ "to_number": "+14155559876" }]
  }'

See Outbound Calling for the full request reference.

​Cartesia Numbers

​Twilio Numbers (Bring Your Own)

​SIP Trunk Numbers (Bring Your Own Carrier)

​Managing Numbers

​Assigning an Inbound Agent

​Outbound-only numbers