context_variables

title	category	tags	difficulty	description	demonstrates
Context Variables	basics	context variables assemblyai openai cartesia	beginner	Shows how to give an agent context about the user using simple variables.	Using context variables from a simple dictionary Formatting instructions with user-specific data

This example shows how to personalize an agent's instructions with user-specific variables. The example injects name, age, and city into the prompt before the session starts.

Prerequisites

• 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 loading your environment variables and setting up logging. Define an AgentServer which wraps your application and handles the worker lifecycle.

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("context-variables")
logger.setLevel(logging.INFO)

server = AgentServer()

Prewarm VAD for faster connections

Preload the VAD model once per process using the setup_fnc.

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

server.setup_fnc = prewarm

Create an agent that accepts context

Build a lightweight agent that formats its instructions with values from a dictionary. If context is passed, the prompt is customized before the agent starts.

class ContextAgent(Agent):
    def __init__(self, context_vars=None) -> None:
        instructions = """
            You are a helpful agent. The user's name is {name}.
            They are {age} years old and live in {city}.
        """

        if context_vars:
            instructions = instructions.format(**context_vars)

        super().__init__(instructions=instructions)

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

Define the RTC session entrypoint

Create the context variables dictionary with user-specific data, then pass it to the agent when starting the session.

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

    context_variables = {
        "name": "Shayne",
        "age": 35,
        "city": "Toronto"
    }

    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,
    )

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

Run the server

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

Run it

python context_variables.py console

How it works

1. Load environment variables and set up logging.
2. Format the agent's instructions with user-specific context variables.
3. Generate an immediate greeting using the personalized prompt when the agent enters.

Full example

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("context-variables")
logger.setLevel(logging.INFO)


class ContextAgent(Agent):
    def __init__(self, context_vars=None) -> None:
        instructions = """
            You are a helpful agent. The user's name is {name}.
            They are {age} years old and live in {city}.
        """

        if context_vars:
            instructions = instructions.format(**context_vars)

        super().__init__(instructions=instructions)

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


server = AgentServer()


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


server.setup_fnc = prewarm


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

    context_variables = {
        "name": "Shayne",
        "age": 35,
        "city": "Toronto"
    }

    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,
    )

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


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