Dynamic variables

Dynamic variables allow you to inject runtime values into your agent’s messages, system prompts, and tools. This enables you to personalize each conversation with user-specific data without creating multiple agents.

Overview

Dynamic variables can be integrated into multiple aspects of your agent:

• System prompts to customize behavior and context
• First messages to personalize greetings
• Tool parameters to pass user-specific data

Here are a few examples where dynamic variables are useful:

• Personalizing greetings with user names
• Including account details in responses
• Passing data to tool calls
• Customizing behavior based on subscription tiers
• Accessing system information like conversation ID or call duration

System dynamic variables

Your agent has access to these automatically available system variables:

• system__agent_id - Unique agent identifier
• system__caller_id - Caller’s phone number (voice calls only)
• system__called_number - Destination phone number (voice calls only)
• system__call_duration_secs - Call duration in seconds
• system__time_utc - Current UTC time (ISO format)
• system__conversation_id - ElevenLabs’ unique conversation identifier
• system__call_sid - Call SID (twilio calls only)

System variables:

• Are available without runtime configuration
• Are prefixed with system__ (reserved prefix)
• In system prompts: Set once at conversation start (value remains static)
• In tool calls: Updated at execution time (value reflects current state)

Guide

Prerequisites

• An ElevenLabs account
• A configured ElevenLabs Conversational Agent (create one here)

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import os
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import signal
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from elevenlabs.client import ElevenLabs
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from elevenlabs.conversational_ai.conversation import Conversation, ConversationConfig
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from elevenlabs.conversational_ai.default_audio_interface import DefaultAudioInterface
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agent_id = os.getenv("AGENT_ID")
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api_key = os.getenv("ELEVENLABS_API_KEY")
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client = ElevenLabs(api_key=api_key)
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dynamic_vars = {
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  "user_name": "Angelo",
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}
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config = ConversationConfig(
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  dynamic_variables=dynamic_vars
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)
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conversation = Conversation(
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  client,
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  agent_id,
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  config=config,
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  # Assume auth is required when API_KEY is set.
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  requires_auth=bool(api_key),
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  # Use the default audio interface.
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  audio_interface=DefaultAudioInterface(),
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  # Simple callbacks that print the conversation to the console.
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  callback_agent_response=lambda response: print(f"Agent: {response}"),
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  callback_agent_response_correction=lambda original, corrected: print(f"Agent: {original} -> {corrected}"),
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  callback_user_transcript=lambda transcript: print(f"User: {transcript}"),
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  # Uncomment the below if you want to see latency measurements.
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  # callback_latency_measurement=lambda latency: print(f"Latency: {latency}ms"),
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)
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conversation.start_session()
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signal.signal(signal.SIGINT, lambda sig, frame: conversation.end_session())

Supported Types

Dynamic variables support these value types:

Troubleshooting