Dynamic Variables
Learn how to personalize your agent’s responses using dynamic variables
Overview
Dynamic variables are a special syntax that allow you to inject data into various parts of the agents for specific call.
They allow you to personalize your agent’s responses while keeping the core conversation flow intact. They’re perfect for customizing greetings, referencing specific information, or adapting responses based on context.
Where can I use them?
- prompt
- begin message
- tool call description
- custom tool call properties description
- voicemail setting (both prompt and static text)
- transfer call function number: in case you want to transfer call to a dynamic number
- warm transfer setting (both prompt and static text)
Add & test dynamic variables
Add dynamic variables in your prompts
Dynamic variables are placeholders surrounded by double curly braces. For example:
Test your dynamic variables
Before deploying, test your dynamic variables using the web interface
Configure agent-level default dynamic variables
You can set default values for dynamic variables at the agent level. Default variables serve as a fallback and will only be used when specific variables aren’t included in the call request.
Implement in production
For Outbound Calls
When using the Create Phone Call API, set your variables in the retell_llm_dynamic_variables
field:
For Inbound Calls
You can supply dynamic variables in the Inbound Call Webhook. More details are at the linked doc.
Default System Variables
Retell automatically provides these system variables - no configuration required:
Variable | Description | Example |
---|---|---|
{{current_agent_state}} | Current state name (for multi-state agents) | “greeting” |
{{previous_agent_state}} | Previous state name | ”qualification” |
{{current_time}} | Current time in America/Los_Angeles | ”Thursday, March 28, 2024 at 11:46:04 PM PST” |
{{current_time_[timezone]}} | Current time in specified timezone , for example: {{current_time_Australia/Sydney}} | ”Thursday, March 28, 2024 at 11:46:04 PM AEDT” |
{{call_type}} | Call type, web_call or phone_call | ”phone_call” |
These variables are only available for phone calls:
Variable | Description | Example |
---|---|---|
{{direction}} | Call direction, inbound or outbound | ”inbound” |
{{user_number}} | User’s phone number (from_number for inbound, to_number for outbound) | “+12137771234” |
{{agent_number}} | Agent’s phone number (to_number for inbound, from_number for outbound) | “+12137771235” |
Edge Cases
When a dynamic variable is not assigned a value, it will remain unchanged in the output. For example:
- Original prompt:
"Hello {{user_name}}, how can I help you today?"
- Output when
user_name
is not set:"Hello {{user_name}}, how can I help you today?"
This means missing variables will be visible in their raw form ({{variable_name}}
) rather than being replaced with an empty string or causing an error.
🎦 Video Tutorial
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