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

# xAI

> xAI Grok TTS provider — expressive multilingual voices with speech tags and auto language detection.

**Voice format:** `xAI.<VoiceId>`

xAI Grok voices are expressive, multilingual text-to-speech voices. They support inline speech tags for pauses, vocal sounds, emphasis, pitch, pace, and intensity.

<Warning>
  xAI Grok voices are higher-latency than [Telnyx Ultra](/docs/voice/tts/providers/telnyx/ultra). For latency-sensitive applications that need sub-100ms time to first byte, use Ultra.
</Warning>

## Voices

| Voice | Voice ID  | Use for                                     |
| ----- | --------- | ------------------------------------------- |
| Ara   | `xAI.ara` | Warm, conversational assistant experiences  |
| Eve   | `xAI.eve` | General-purpose voice assistant experiences |
| Leo   | `xAI.leo` | Confident, direct interactions              |
| Rex   | `xAI.rex` | Characterful or energetic interactions      |
| Sal   | `xAI.sal` | Distinctive conversational tone             |

***

## WebSocket

xAI Grok voices are not available on the public TTS WebSocket API. Use the [REST API](/docs/voice/tts/rest-api) for direct text-to-speech generation, or use xAI Grok voices with [AI Assistants](/docs/inference/ai-assistants/no-code-voice-assistant).

## REST API

### Fields

| Field           | Type    | Default         | Description                                       |
| --------------- | ------- | --------------- | ------------------------------------------------- |
| `language`      | string  | `auto`          | Language code, or `auto` to detect automatically. |
| `output_format` | string  | `mp3`           | `mp3`, `wav`, `pcm`, `mulaw`, or `alaw`.          |
| `sample_rate`   | integer | `24000`         | 8000, 16000, 22050, 24000, 44100, or 48000.       |
| `output_type`   | string  | `binary_output` | `binary_output`, `base64_output`, or `audio_id`.  |

```json theme={null}
{
  "text": "Let me check that for you. [pause] I found your appointment.",
  "voice": "xAI.eve",
  "voice_settings": {
    "language": "auto",
    "output_format": "mp3",
    "sample_rate": 24000
  }
}
```

### Response

Default (`binary_output`): chunked audio bytes.

With `output_type: "base64_output"`: JSON with base64-encoded audio.

With `output_type: "audio_id"`: JSON with an `audio_url` for deferred retrieval.

## Expressive speech tags

Use speech tags inline in `text` when you want more expressive delivery.

| Tag                                          | Use for                                                   |
| -------------------------------------------- | --------------------------------------------------------- |
| `[pause]`                                    | A short natural pause                                     |
| `[long-pause]`                               | A longer pause for topic transitions or important moments |
| `[laugh]`, `[chuckle]`, `[giggle]`           | Natural laughter or amused reactions                      |
| `[sigh]`, `[breath]`, `[inhale]`, `[exhale]` | Breath and sigh sounds                                    |
| \<whisper>                                   | Whispered delivery                                        |
| \<soft>                                      | Softer delivery                                           |
| \<loud>                                      | Louder delivery                                           |
| \<emphasis>                                  | Emphasized delivery                                       |
| \<slow>, \<fast>                             | Slower or faster pace                                     |
| \<higher-pitch>, \<lower-pitch>              | Higher or lower pitch                                     |

```text theme={null}
So I walked in and [pause] there it was. [laugh] I honestly could not believe it!
```

```text theme={null}
<emphasis>Your appointment is confirmed for tomorrow at 3 PM.</emphasis>
```

<Tip>
  Use expressive tags sparingly. The goal is natural delivery, not tagging every sentence.
</Tip>

## AI Assistants

For AI Assistants, choose an xAI Grok voice such as `xAI.eve` and enable **Expressive Mode** to let the assistant decide when speech tags improve the caller experience.

<CardGroup cols={2}>
  <Card title="AI Assistants" icon="robot" href="/docs/inference/ai-assistants/no-code-voice-assistant">
    Build voice AI assistants using xAI Grok voices with Expressive Mode.
  </Card>

  <Card title="TTS REST API" icon="code" href="/docs/voice/tts/rest-api">
    Generate speech directly with REST TTS requests.
  </Card>
</CardGroup>