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Transfer an active call to any E.164 phone number or department via SIP REFER from a LiveKit AI agent.

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Clone and run the full working example

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Getting started

git clone https://github.com/vobiz-ai/Vobiz-Livekit-Call-Transfer-Example.git
cd Vobiz-Livekit-Call-Transfer-Example
pip install -r requirements.txt
python agent.py dev

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Overview

The AI agent handles the conversation and, when instructed, performs a cold SIP REFER transfer to any phone number. The agent constructs the SIP URI dynamically - the caller is transferred and the agent disconnects.

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How it works

  1. Caller requests a transfer (e.g. “Transfer me to sales” or “Transfer me to +1 555 000 1234”).
  2. The agent calls the transfer_call function tool.
  3. The agent sends a SIP REFER to sip:+15550001234@your-vobiz-domain.
  4. Vobiz routes the call to the destination.
  5. The agent leaves the room - the transfer is complete.

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Agent function tool

@llm.function_tool(description="Transfer the caller to an E.164 phone number directly")
async def transfer_call(context: llm.FunctionContext, phone_number: str):
    sip_uri = f"sip:{phone_number}@{VOBIZ_SIP_DOMAIN}"
    await context.room.local_participant.perform_rpc(
        destination_identity="sip",
        method="transfer",
        payload=sip_uri
    )

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Preset department transfers

Configure preset destinations in .env and map them to named tools:
CommandDestination
”Transfer to billing”BILLING_NUMBER
”Transfer to support”SUPPORT_NUMBER
”Transfer me to [number]“Any E.164 number

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Environment variables

.env
LIVEKIT_URL=wss://your-project.livekit.cloud
LIVEKIT_API_KEY=APIxxxxxxxxxxxxx
LIVEKIT_API_SECRET=secretxxxxxxxxxx
VOBIZ_SIP_DOMAIN=your-domain.sip.vobiz.ai
OPENAI_API_KEY=sk-...
BILLING_NUMBER=+919XXXXXXXXX
SUPPORT_NUMBER=+919XXXXXXXXX