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

# synthesize_speech

> Generate an MP3 speech sample with Rime TTS via the MCP server, rendered in an inline audio player.

Generate an MP3 speech sample from text. All arguments are optional: with none, it plays a default sample in the demo voice (`lyra` on **Coda**, Rime's flagship model) — the fastest way to hear Rime. Choose a `speaker` and `modelId` from [`list_voices`](/mcp-reference/list-voices) and [`get_voice_details`](/mcp-reference/get-voice-details).

**API key:** Required — see [Authentication](/mcp-reference/authentication). Samples consume credits like any other API request, so keep sample text short.

## Parameters

| Parameter       | Type    | Required | Default           | Description                                                                                                                                                                |
| --------------- | ------- | -------- | ----------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `text`          | string  | No       | A short demo line | Text to synthesize (max 2,000 characters)                                                                                                                                  |
| `speaker`       | string  | No       | `lyra`            | Voice name from [`list_voices`](/mcp-reference/list-voices)                                                                                                                |
| `modelId`       | string  | No       | `coda`            | Model ID: `coda` (flagship), `mistv3`, or `arcana`                                                                                                                         |
| `language`      | string  | No       | —                 | Sent as `lang` only if provided (e.g. `eng`, the value from [`get_voice_details`](/mcp-reference/get-voice-details)). Omit to let Rime infer the language from the speaker |
| `include_audio` | boolean | No       | `false`           | Also return the audio as a standard MCP audio content block (base64), for hosts that play audio natively. Adds the audio to the model's context                            |

## Returns

Audio is delivered three ways so it plays regardless of the host — an inline player in UI hosts, a short-lived play URL (`structuredContent.audioUrl`) for terminal hosts, and an optional audio content block. See [Playing audio](/mcp-reference/audio).

## Example

Ask your assistant:

```
Play me a sample of the astra voice saying "Thanks for calling, how can I help?"
```

## Related

* [Playing audio](/mcp-reference/audio) — how samples reach your speakers in each host
* [Models](/docs/models) — compare Coda, Mist v3, and Arcana
* [Streaming APIs](/docs/streaming) — production synthesis