Number Pooling

Number pooling lets one agent use several phone numbers at once. An inbound agent answers calls to any number in its pool. An outbound agent can place each call from a different number in its pool, so you can route traffic by campaign, region, or brand while keeping one agent configuration.

Pooled numbers can be numbers bought in Synthflow, custom numbers, or numbers from your imported Twilio account.

Attached numbers

Open the deployment settings of a voice agent and select Phone to see every number in its pool. The agent editor header shows the first number plus a count of the others, such as +2.

Get agent returns the same numbers in attached_phone_numbers:

{
  "attached_phone_numbers": [
    {
      "number": "+16286666348",
      "sid": "PN9c8dba0c87f9173af8054d3ccedb8afd",
      "slug": "16286666348"
    }
  ]
}

Use slug to detach a number. Use number to choose the caller ID for an outbound call.

Adding numbers

Select Add Phone Number under Phone to add a number to the pool. Through the API, Attach phone numbers adds one or more at once. Identify them either by phone number in E.164 format or by slug, not both in the same request.

A number can serve only one inbound agent at a time, but it can be in the pool of several outbound agents.

Removing a number

Select the remove icon next to a number under Phone to take it out of the pool. Through the API, Detach phone number removes one number by its slug.

The number stops routing calls to the agent as soon as it is removed. Calls to it no longer reach the agent, and the agent can no longer place calls from it. The number stays in your workspace, ready to attach to another agent.

Outbound caller ID

An outbound agent marks one number in its pool Default. Calls that do not set a caller ID use it. Removing the Default number makes the next oldest number the Default. Inbound agents have no Default.

Make a call takes an optional from_phone_number, which sets the caller ID for that call. It must be a number in the agent’s pool.

{
  "model_id": "0ae2859d-c25c-4d56-a9f3-809387b725ce",
  "phone": "+14155550123",
  "name": "John Doe",
  "from_phone_number": "+16286666348"
}

For a Phone call test, Call from picks the caller ID when the agent has two or more numbers. It starts on the Default number and resets to it after a reload.

Call logs show the number each call was placed from, so you can check which caller ID was used.

FAQ