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# addInternalFiller

> Add filler phrases for a specific native SWAIG function and language.

[ref-agentbase]: /docs/server-sdks/reference/typescript/agents/agent-base

Add filler phrases spoken while a specific native SWAIG function is executing. The AI
randomly selects from the list each time the function is invoked.

> **Note**
>
> Only a fixed set of native function names accept fillers: `hangup`, `check_time`,
> `wait_for_user`, `wait_seconds`, `adjust_response_latency`, `next_step`,
> `change_context`, `get_visual_input`, `get_ideal_strategy`. Passing any other name
> logs a warning and is silently ignored by the runtime.

## **Parameters**

**`functionName`** `string` — required

One of the supported native function names (e.g., `"next_step"`, `"check_time"`).
Unknown names log a warning and are ignored.

---

**`languageCode`** `string` — required

BCP-47 language code (e.g., `"en-US"`, `"es"`, `"fr"`).

---

**`fillers`** `string[]` — required

Array of filler phrases for this function and language.

---

## **Returns**

[`AgentBase`][ref-agentbase] -- Returns `this` for method chaining.

## **Example**

```typescript {5}
import { AgentBase } from '@signalwire/sdk';

const agent = new AgentBase({ name: 'support', route: '/support' });
agent.setPromptText('You are a helpful assistant.');
agent.addInternalFiller(
  'next_step', 'en-US',
  ['Moving to the next step...', 'Great, let\'s continue...'],
);
agent.addInternalFiller(
  'next_step', 'es',
  ['Pasando al siguiente paso...', 'Continuemos...'],
);
await agent.serve();
```

> Add filler phrases for a specific native SWAIG function and language.