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

# Template variables

> Use the supported double-curly syntax to insert runtime values into prompts, request bodies, headers, and other configurable fields.

Use the supported double-curly syntax to insert runtime values into prompts, request bodies, headers, and other configurable fields.

## Prerequisites

* A workflow with a known source for each value.
* A test case that supplies the same scope and shape at runtime.

## Use supported syntax

1. Open a prompt, tool field, or payload template.
2. Insert a simple value with `{{name}}`.
3. Use scoped values such as `{{initial_context.phone_number}}` or `{{gathered_context.preference}}`.
4. Use a default when a value can be absent, for example `{{name | default}}`.
5. Test the rendered result before publishing.

## Supported scopes

Initial context contains values available at call start. Gathered context contains values extracted during the call. Other runtime metadata is available only where the owning field supports it.

## Constraints and failure states

Variable names are case-sensitive contracts between the producer and consumer. A template cannot create a missing value; provide the value through initial context, pre-call data, or extraction before relying on it.

## Protect your data

Templates can place values into spoken audio, outbound requests, or logs. Avoid rendering secrets and restrict fields to the intended audience.

## Related

* [Context and variables](/core-concepts/context-and-variables)
* [Pre-call data fetch](/voice-agent/pre-call-data-fetch)
* [Webhook node](/voice-agent/webhook)


## Related topics

- [Context and variables](/core-concepts/context-and-variables.md)
- [API Trigger node](/voice-agent/api-trigger.md)
- [HTTP tool configuration](/voice-agent/tools/http-api.md)
- [Webhook node](/voice-agent/webhook.md)
- [Pre-call data fetch](/voice-agent/pre-call-data-fetch.md)