Transfer to a human

transfer_to_human is a built-in tool your AI agent can invoke mid-call to hand the caller to a person. You enable it on the agent and give it one destination number; the agent decides when to use it.

Configure the destination

{
  "type": "builtin",
  "name": "transfer_to_human",
  "phone_number": "+12025550100"
}

phone_number is required whenever the tool is enabled, and must be full E.164 — a leading +, then the country code. A blank, partial, or non-dialable number is rejected when you create or update the agent, so a misconfigured transfer surfaces at save time instead of failing in front of a caller.

Note that a bare national number is not accepted even when it looks unambiguous: 2025550100 is not the same request as +12025550100, and guessing a country code on your behalf is how a call ends up dialing a real number in a different country.

When the agent decides to transfer

There is no fixed rule, hour, or condition that triggers a transfer. The agent calls the tool on its own judgment, from its instructions and the conversation so far — so the way you steer transfers is the agent's own prompt. If you want a transfer only for billing disputes, or only after the caller asks twice, say so in the instructions.

The tool takes an optional reason, which the agent supplies to describe why it handed the call over.

What the tool reports back

The tool returns once the transfer has been requested — that is not the same as a person having answered. Treat a successful tool call as "the handoff was started," and read call evidence for what actually happened on the call.