Transfer to human
Seamlessly transfer the user to a human operator via phone number based on defined conditions.
Overview
Human transfer allows a Conversational AI agent to transfer the ongoing call to a specified phone number when certain conditions are met. This enables agents to hand off complex issues, specific requests, or situations requiring human intervention to a live operator.
This feature utilizes the transfer_to_number
system tool which supports transfers via Twilio and SIP trunk numbers. When triggered, the agent can provide a message to the user while they wait and a separate message summarizing the situation for the human operator receiving the call.
Numbers that can be transferred to
Currently only SIP trunking phone numbers support transferring to external numbers. Twilio phone numbers currently can only transfer to phone numbers hosted on Twilio. If this is needed we recommended using Twilio numbers via Twilio elastic SIP trunking and our SIP trunking support, rather than via the native integration.
Enabling human transfer
Human transfer is configured using the transfer_to_number
system tool.
Add the transfer tool
Enable human transfer by selecting the transfer_to_number
system tool in your agent’s configuration within the Agent
tab. Choose “Transfer to Human” when adding a tool.

Configure tool description (optional)
You can provide a custom description to guide the LLM on when to trigger a transfer. If left blank, a default description encompassing the defined transfer rules will be used.

Define transfer rules
Configure the specific rules for transferring to phone numbers. For each rule, specify:
- Phone Number: The target phone number in E.164 format (e.g., +12125551234) to transfer the call to.
- Condition: A natural language description of the circumstances under which the transfer should occur (e.g., “User explicitly requests to speak to a human”, “User needs to update sensitive account information”).
The LLM will use these conditions, along with the tool description, to decide when and to which phone number to transfer.

Ensure the phone number is correctly formatted (E.164) and associated with a properly configured Twilio account capable of receiving calls.
API Implementation
You can configure the transfer_to_number
system tool when creating or updating an agent via the API. The tool allows specifying messages for both the client (user being transferred) and the agent (human operator receiving the call).