### Using variables in your prompt

To set up dynamic variables, first include placeholders for them in your system prompt. Use double curly braces ({{variable_name}}) to mark where each variable should appear in the text. This allows EVI to replace these placeholders dynamically with the specified values.

### Sample prompt with dynamic variables

```
Address the user by their name, {{name}}.
If relevant, reference their age: {{age}}.
It is {{is_philosopher}} that this user is a philosopher.
```

### Assigning values in session settings

After adding placeholders for dynamic variables in your prompt, set their values by sending a Session Settings message over the WebSocket within an active Chat session. This message includes a variables parameter, with each key matching a placeholder in your prompt and each value specifying the text EVI will use.

### Session settings

```
{
  "type": "session_settings",
  "variables": {
    "name": "David Hume",
    "age": 65,
    "is_philosopher": true
  }
}
```

### Default dynamic variables

Hume provides built-in dynamic variables that are automatically populated and can be referenced in system prompts without needing to set their values in SessionSettings. The currently supported default variable is:

- **now**: The current UTC datetime (e.g., "Nov 08, 2024 09:25 PM UTC")

You can reference `now` in your system prompt to dynamically include the current UTC date and time.