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

# System Variables

> Built-in call and agent variables available in every session

System variables are automatically populated at the start of every call. They give you dynamic, call-specific data you can reference in messages, node fields, logic flows, and integrations without setting them yourself.

## Available variables

| Variable               | Description                                                      |
| ---------------------- | ---------------------------------------------------------------- |
| `{{caller}}`           | Unique identifier for the caller in this session.                |
| `{{agent_name}}`       | Name of the agent handling the call.                             |
| `{{agent_id}}`         | Unique ID of the agent.                                          |
| `{{agent_version_id}}` | Unique ID of the published agent version that handled the call.  |
| `{{organization}}`     | Unique ID of the organization the agent belongs to.              |
| `{{call_id}}`          | Unique ID of the current call.                                   |
| `{{started_at}}`       | Timestamp when the call started.                                 |
| `{{ended_at}}`         | Timestamp when the call ended.                                   |
| `{{duration}}`         | Call duration (e.g. `29s`).                                      |
| `{{call_summary}}`     | AI-generated summary of the call. Available after the call ends. |

<Warning>
  `{{call_summary}}` requires **Post-Call Analysis** to be enabled in **Settings**. If it is not enabled, the value will be `"Not available"`.
</Warning>

## Usage

Reference any system variable using double curly braces anywhere a node field accepts dynamic values: messages, email bodies, webhook payloads, integration parameters, and more.

```
Hi, this is a summary of your call with {{agent_name}}.

Call ID: {{call_id}}
Started: {{started_at}}
Duration: {{duration}}

Summary: {{call_summary}}
```

System variables follow the same syntax as user-defined variables. See [Variables](/configure/variables) for how variables work across flows.