Documentation 2026-07-04 20:00 UTC to 2026-07-06 22:58 UTC

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3# Text to Speech3# Text to Speech

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5Convert text into spoken audio with a single API call. The API supports 5 expressive voices, inline speech tags for fine-grained delivery control, and output formats from high-fidelity MP3 to telephony-optimized μ-law.5Convert text into spoken audio with a single API call. The API supports a rich set of expressive voices, inline speech tags for fine-grained delivery control, and output formats from high-fidelity MP3 to telephony-optimized μ-law.

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7## Quick Start7## Quick Start

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128 128 

129## Voices129## Voices

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131Five voices are available, each with a distinct personality. Listen to samples and choose the best fit for your use case:131Each voice has a distinct personality. Listen to samples and choose the best fit for your use case (`eve` is the default):

132 

133| Voice | Tone | Description | Sample |

134|-------|------|-------------|:------:|

135| **`eve`** | Energetic, upbeat | Default voice - engaging and enthusiastic | |

136| **`ara`** | Warm, friendly | Balanced and conversational | |

137| **`rex`** | Confident, clear | Professional and articulate - ideal for business | |

138| **`sal`** | Smooth, balanced | Versatile voice for a wide range of contexts | |

139| **`leo`** | Authoritative, strong | Commanding and decisive - great for instructional content | |

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141Voice IDs are **case-insensitive** - `eve`, `Eve`, and `EVE` all work. [Preview all voices in the playground →](https://console.x.ai/team/default/voice/text-to-speech?campaign=voice-docs-tts)133Voice IDs are **case-insensitive** - `eve`, `Eve`, and `EVE` all work. [Preview all voices in the playground →](https://console.x.ai/team/default/voice/text-to-speech?campaign=voice-docs-tts)

142 134 

143### Choosing the right voice

144 

145* **`eve`** - Great default for demos, announcements, and upbeat content

146* **`ara`** - Ideal for conversational interfaces, customer support, and warm narration

147* **`rex`** - Best for business presentations, corporate communications, and tutorials

148* **`sal`** - Versatile choice for balanced delivery across different content types

149* **`leo`** - Perfect for authoritative narration, instructions, and educational content

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151### Custom voices135### Custom voices

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153Clone any voice from a short reference clip with the [Custom Voices API](/developers/model-capabilities/audio/custom-voices), or create one for free in the [console](https://console.x.ai/team/default/voice/voice-library?campaign=voice-docs-tts). To find your custom voice ID in the console, click the three-dot menu on the voice card and select **Copy Voice ID**. Then pass it as `voice_id`:137Clone any voice from a short reference clip with the [Custom Voices API](/developers/model-capabilities/audio/custom-voices), or create one for free in the [console](https://console.x.ai/team/default/voice/voice-library?campaign=voice-docs-tts). To find your custom voice ID in the console, click the three-dot menu on the voice card and select **Copy Voice ID**. Then pass it as `voice_id`:

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74## Text to Speech74## Text to Speech

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76Convert text to spoken audio in 5 expressive voices. Inline speech tags (laughter, whispers, pauses) and output formats from high-fidelity MP3 to telephony μ-law. Unary requests or WebSocket streaming.76Convert text to spoken audio with a large roster of expressive voices. Inline speech tags (laughter, whispers, pauses) and output formats from high-fidelity MP3 to telephony μ-law. Unary requests or WebSocket streaming.

77 77 

78```bash78```bash

79curl -X POST https://api.x.ai/v1/tts \79curl -X POST https://api.x.ai/v1/tts \

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265## Voices265## Voices

266 266 

267When using the Voice Agent API or Text to Speech, you can choose between 5 distinct voices. Each has its own personality and tone, so pick the one that best fits your application — from upbeat and conversational to authoritative and instructional.267When using the Voice Agent API or Text to Speech, you can choose from the full set of built-in voices. Each has its own personality and tone, so pick the one that best fits your application (`eve` is the default):

268 

269| Voice | Type | Tone | Description | Sample |

270| --------- | ------- | --------------------- | ----------------------------------------------------------- | :-----------------------------------------------------------------: |

271| **`eve`** | Female | Energetic, upbeat | Default voice, engaging and enthusiastic | |

272| **`ara`** | Female | Warm, friendly | Balanced and conversational | |

273| **`rex`** | Male | Confident, clear | Professional and articulate, ideal for business | |

274| **`sal`** | Neutral | Smooth, balanced | Versatile voice suitable for various contexts | |

275| **`leo`** | Male | Authoritative, strong | Decisive and commanding, suitable for instructional content | |

276 268 

277### Enterprise Compliance & Security269### Enterprise Compliance & Security

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148|-----------|------|-------------|148|-----------|------|-------------|

149| `instructions` | string | System prompt |149| `instructions` | string | System prompt |

150| `reasoning.effort` | `"high"` | `"none"` | optional | Controls whether the model uses reasoning. Defaults to `"high"`. Supported only with `grok-voice-latest` and `grok-voice-think-fast-1.0`. |150| `reasoning.effort` | `"high"` | `"none"` | optional | Controls whether the model uses reasoning. Defaults to `"high"`. Supported only with `grok-voice-latest` and `grok-voice-think-fast-1.0`. |

151| `voice` | string | Voice selection: `eve`, `ara`, `rex`, `sal`, `leo`, or a [custom voice ID](/developers/model-capabilities/audio/custom-voices) (see [Available Voices](#available-voices)) |151| `voice` | string | Voice selection: any built-in voice (e.g. `eve`, the default) or a [custom voice ID](/developers/model-capabilities/audio/custom-voices) (see [Available Voices](#available-voices)) |

152| `tools` | array | Tools available to the voice agent. Supports `file_search`, `web_search`, `x_search`, `mcp`, and `function` types. See [Using Tools](#using-tools-with-grok-voice-agent-api). |152| `tools` | array | Tools available to the voice agent. Supports `file_search`, `web_search`, `x_search`, `mcp`, and `function` types. See [Using Tools](#using-tools-with-grok-voice-agent-api). |

153| `turn_detection.type` | string | null | `"server_vad"` for automatic detection, `null` for manual text turns |153| `turn_detection.type` | string | null | `"server_vad"` for automatic detection, `null` for manual text turns |

154| `turn_detection.threshold` | number | optional | VAD activation threshold (0.1–0.9). Higher values require louder audio to trigger. Default: `0.85`. |154| `turn_detection.threshold` | number | optional | VAD activation threshold (0.1–0.9). Higher values require louder audio to trigger. Default: `0.85`. |

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167## Available Voices167## Available Voices

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169| Voice | Type | Tone | Description | Sample |169The same roster of voices works across the Voice Agent API and Text to Speech API. Browse the full list with tone descriptions and samples in the [voice table](/developers/model-capabilities/audio/text-to-speech#voices), or fetch it programmatically via [`GET /v1/tts/voices`](/developers/rest-api-reference/inference/voice). Pass the lowercase voice ID as the `voice` parameter on `session.update`.

170|-------|------|------|-------------|:------:|

171| **`eve`** | Female | Energetic, upbeat | Default voice, engaging and enthusiastic | |

172| **`ara`** | Female | Warm, friendly | Balanced and conversational | |

173| **`rex`** | Male | Confident, clear | Professional and articulate, ideal for business applications | |

174| **`sal`** | Neutral | Smooth, balanced | Versatile voice suitable for various contexts | |

175| **`leo`** | Male | Authoritative, strong | Decisive and commanding, suitable for instructional content | |

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177### Custom Voices171### Custom Voices

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40| grok-4.20-multi-agent-0309 | T0: 7, T1: 10, T2: 15, T3: 25, T4: 45 | T0: 2.5M, T1: 3.7M, T2: 6.2M, T3: 11M, T4: 21M |40| grok-4.20-multi-agent-0309 | T0: 7, T1: 10, T2: 15, T3: 25, T4: 45 | T0: 2.5M, T1: 3.7M, T2: 6.2M, T3: 11M, T4: 21M |

41| grok-imagine-image-quality | 5 | — |41| grok-imagine-image-quality | 5 | — |

42| grok-imagine-image | 5 | — |42| grok-imagine-image | 5 | — |

43| grok-imagine-video | 1 | — |

44| grok-imagine-video-1.5 | 1 | — |43| grok-imagine-video-1.5 | 1 | — |

44| grok-imagine-video | 1 | — |

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46### What counts toward TPM46### What counts toward TPM

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