# Template Interpolation Agent, Say Node & Menu Node

### Template Interpolation

Text fields (Say, Agent, Menu prompts) use {{expression}} interpolation:

<table data-header-hidden><thead><tr><th valign="top"></th><th valign="top"></th><th valign="top"></th></tr></thead><tbody><tr><td valign="top">Syntax</td><td valign="top">Purpose</td><td valign="top">Example</td></tr><tr><td valign="top">{{expression}}</td><td valign="top">Variable lookup or expression</td><td valign="top">Hello {{name}}, you have {{items.length}} items</td></tr></tbody></table>

* {{expression}} — evaluated by the Expression Engine, matches the next }}
* Simple variable names like {{name}} resolve to a variable lookup
* Complex expressions like {{items.filter(x => x.active).length}} are fully evaluated
* The double-brace delimiter avoids collision with JSON content in system prompts
* Non-printable results (objects, arrays) are JSON-stringified; null/undefined produce empty\
  string
* Errors preserve the original text and log a warning

### What Template Interpolation Means in an Agent Node, Say Node and Menu Node

* Configure an **Agent Node**&#x20;
* Inside the **System Prompt** field, you typed:\
  `Testing {{`
* As soon as `{{` is typed, a **template helper dropdown** appears
* The dropdown lists:
  * **Variables** (`var boolean`, `var number`, `var userEndpoint`, etc.)
  * **Slots from Test (agent node)** (example tooltip: *Variable – boolean*)
  * **Built‑in functions** (`fn $addDays`, `fn $format`, `fn $now`, etc.)
  * **JS native objects/functions** (`Date`, `Math`, `parseInt`, `String`, etc.)

This confirms that **the System Prompt supports template interpolation using `{{ }}` syntax**, with access to typed variables and runtime helpers.

<figure><img src="/files/3svOGhTQrzQXroAYlZep" alt=""><figcaption></figcaption></figure>


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