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Simple Call Answering Agent

Basic agent for handling incoming phone calls with simple conversation

This example is a basic agent that can answer inbound phone calls. This doesn't require any SIP-specific code. When you point a LiveKit phone number at a dispatch rule, SIP callers are automatically delivered into the room and the running agent greets them.

Prerequisites

  • Buy a phone number in the LiveKit dashboard and create a dispatch rule that targets your worker:
    • Buy a number: Telephony → Phone Numbers → Buy number → Create dispatch rule
  • Add a .env in this directory with your LiveKit credentials:
    LIVEKIT_URL=your_livekit_url
    LIVEKIT_API_KEY=your_api_key
    LIVEKIT_API_SECRET=your_api_secret
  • Install dependencies:
    pip install "livekit-agents[silero]" python-dotenv

Load environment, logging, and define an AgentServer

Start by importing the necessary modules and setting up the basic agent server. Load environment variables and configure logging for debugging.

import logging
from dotenv import load_dotenv
from livekit.agents import JobContext, JobProcess, Agent, AgentSession, AgentServer, cli, inference
from livekit.plugins import silero


load_dotenv()


logger = logging.getLogger("answer-call")
logger.setLevel(logging.INFO)


server = AgentServer()

Define the agent and session

Keep your Agent lightweight by only including the instructions. Preload VAD so that it runs once per process to cut down on connection latency.

Define STT, LLM, and TTS as a part of your AgentSession inside the RTC session. Start your session with your agent and connect to the room.

import logging
from dotenv import load_dotenv
from livekit.agents import JobContext, JobProcess, Agent, AgentSession, AgentServer, cli, inference
from livekit.plugins import silero


load_dotenv()


logger = logging.getLogger("answer-call")
logger.setLevel(logging.INFO)


server = AgentServer()


def prewarm(proc: JobProcess):
    proc.userdata["vad"] = silero.VAD.load()


server.setup_fnc = prewarm


class SimpleAgent(Agent):
    def __init__(self) -> None:
        super().__init__(
            instructions="""
                You are a helpful agent.
            """
        )


    async def on_enter(self):
        self.session.generate_reply()




@server.rtc_session()
async def my_agent(ctx: JobContext):
    ctx.log_context_fields = {"room": ctx.room.name}


    session = AgentSession(
        stt=inference.STT(model="deepgram/nova-3-general"),
        llm=inference.LLM(model="openai/gpt-4.1-mini"),
        tts=inference.TTS(model="cartesia/sonic-3", voice="9626c31c-bec5-4cca-baa8-f8ba9e84c8bc"),
        vad=ctx.proc.userdata["vad"],
        preemptive_generation=True,
    )
    agent = SimpleAgent()


    await session.start(agent=agent, room=ctx.room)
    await ctx.connect()

Run the server

The cli.run_app() function starts the agent server. It manages the worker lifecycle, connects to LiveKit, and processes incoming jobs. When you run the script, it listens for incoming calls and automatically spawns agent sessions when calls arrive.

import logging
from dotenv import load_dotenv
from livekit.agents import JobContext, JobProcess, Agent, AgentSession, AgentServer, cli, inference
from livekit.plugins import silero


load_dotenv()


logger = logging.getLogger("answer-call")
logger.setLevel(logging.INFO)


server = AgentServer()


def prewarm(proc: JobProcess):
    proc.userdata["vad"] = silero.VAD.load()


server.setup_fnc = prewarm


class SimpleAgent(Agent):
    def __init__(self) -> None:
        super().__init__(
            instructions="""
                You are a helpful agent.
            """
        )


    async def on_enter(self):
        self.session.generate_reply()


@server.rtc_session()
async def my_agent(ctx: JobContext):
    ctx.log_context_fields = {"room": ctx.room.name}


    session = AgentSession(
        stt=inference.STT(model="deepgram/nova-3-general"),
        llm=inference.LLM(model="openai/gpt-4.1-mini"),
        tts=inference.TTS(model="cartesia/sonic-3", voice="9626c31c-bec5-4cca-baa8-f8ba9e84c8bc"),
        vad=ctx.proc.userdata["vad"],
        preemptive_generation=True,
    )
    agent = SimpleAgent()


    await session.start(agent=agent, room=ctx.room)
    await ctx.connect()


if __name__ == "__main__":
    cli.run_app(server)

Run it

Run the agent using the console command, which starts the agent in console mode. This mode is useful for testing and debugging. It connects to a mocked LiveKit room so you can test the agent locally before deploying. This will not work for real phone calls (since the room is mocked), but it's a great way to quickly test that your agent works.

python answer_call.py console

If you want to test your agent with a real phone call, you'll need to start it in dev mode instead. This will connect your agent to a LiveKit server, which makes it available to your dispatch rules.

python answer_call.py dev

How inbound calls connect

  1. An inbound call hits your LiveKit number.
  2. The dispatch rule attaches the SIP participant to your room.
  3. If the worker is running, the agent is already in the room and responds immediately—no special SIP handling needed.

Complete code for the call answering agent

import logging
from dotenv import load_dotenv
from livekit.agents import JobContext, JobProcess, Agent, AgentSession, AgentServer, cli, inference
from livekit.plugins import silero


load_dotenv()


logger = logging.getLogger("answer-call")
logger.setLevel(logging.INFO)


server = AgentServer()


def prewarm(proc: JobProcess):
    proc.userdata["vad"] = silero.VAD.load()


server.setup_fnc = prewarm


class SimpleAgent(Agent):
    def __init__(self) -> None:
        super().__init__(
            instructions="""
                You are a helpful agent.
            """
        )


    async def on_enter(self):
        self.session.generate_reply()




@server.rtc_session()
async def my_agent(ctx: JobContext):
    ctx.log_context_fields = {"room": ctx.room.name}


    session = AgentSession(
        stt=inference.STT(model="deepgram/nova-3-general"),
        llm=inference.LLM(model="openai/gpt-4.1-mini"),
        tts=inference.TTS(model="cartesia/sonic-3", voice="9626c31c-bec5-4cca-baa8-f8ba9e84c8bc"),
        vad=ctx.proc.userdata["vad"],
        preemptive_generation=True,
    )
    agent = SimpleAgent()


    await session.start(agent=agent, room=ctx.room)
    await ctx.connect()


if __name__ == "__main__":
    cli.run_app(server)
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