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

# Variables and default values

> Personalize greetings and agent instructions with reusable variables.

Variables let you use the same agent instructions with different customer and conversation
details. Add a variable reference to a greeting or prompt, then provide its value when the
conversation runs or set a default value in the agent.

## Add a variable reference

Use double braces around a variable key:

```text theme={"dark"}
Hello {{customer_name}}! How can I help you today?
```

Use clear, reusable keys such as `customer_name`, `appointment_type`, or `order_id`. Keep the
key consistent everywhere you use it.

When Vocily finds a variable reference in your greeting or prompt, it shows the key in
**Prompt Variables & Defaults** in Agent Core.

## Create an agent variable

1. Open the agent in [Agent Studio](/building-agents/overview).
2. Open [Agent Core](/building-agents/agent-core).
3. Scroll to **Prompt Variables & Defaults**.
4. Select **Add**.
5. Enter the variable **Key**.
6. Enter an optional **Default Value**.
7. Select **Add Variable**.

The key is used inside the prompt as `{{key}}`. For example, a variable with the key
`customer_name` is written as `{{customer_name}}`.

## Set or change a default value

If a variable already appears in the prompt, select **Add Default** beside it to set a value.
To change an existing value:

1. Open **Prompt Variables & Defaults**.
2. Select the edit control beside the variable.
3. Update **Default Value**.
4. Select **Save Variable**.

The panel shows **No default value set** when a variable does not have one. Use a default when
the agent should have a sensible value available even when a conversation does not provide a
specific value.

## Use variables in greetings and prompts

Variables are useful when the agent should refer to a known detail without asking for it again.
For example:

```text theme={"dark"}
Hi {{customer_name}}. I can help with your {{appointment_type}} appointment.
```

Keep instructions for the variable's meaning in **Agent Purpose** or **Call Flow**. A variable
provides a value; your prompt tells the agent how to use that value.

## Use data from tools and automations

Connected tools and API automations can make additional data available to the agent. You can
reference that data in the prompt using the suggestions shown by the editor. Configure those
connections in [Capabilities](/building-agents/capabilities).

Use [Test](/test/overview) after adding a variable to check that the greeting and prompt use it
as expected.

## Edit or remove a variable

* Select the edit control to change its default value.
* Select the delete control to remove a deletable variable.

If a variable is still referenced by a greeting, prompt, or tool, update those references before
removing it.

## What's next

* Define how your agent uses the value in [Agent Core](/building-agents/agent-core).
* Add knowledge bases and tools in [Capabilities](/building-agents/capabilities).
* Test the updated greeting and conversation flow in [Test](/test/overview).