> ## Documentation Index
> Fetch the complete documentation index at: https://docs.persistence.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Dynamic variables

> Personalize calls and carry structured values through prompts, flows, and actions.

Dynamic variables let one agent use call-specific values such as a caller name, account reference, campaign attribute, or action result.

## Variable sources

A value can come from:

* Defaults configured on the agent
* Test values entered for a preview
* Recipient metadata supplied for an outbound call or campaign
* An inbound webhook response
* An extraction or action result during the conversation

## Use variables safely

Give every required variable a default so the draft can be saved and previews remain predictable. Use a neutral fallback rather than a fake production value.

Reference variables only in fields that support them, such as instructions, greetings, action requests, and flow conditions. Keep credentials in [Secrets](/accounts/secrets), not dynamic variables.

## Test missing and malformed values

Run a preview with the expected value, an empty value, an unexpected value, and characters that need pronunciation. Confirm that the agent does not expose raw placeholders or take an unsafe branch.