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

# SpeechRequest

Text-to-speech request input

## Fields

| Field             | Type                                                                                                | Required             | Description                                                                                                                                                                                                                                                                                                             | Example                                                                                                                                                                                                                     |
| ----------------- | --------------------------------------------------------------------------------------------------- | -------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `Input`           | `string`                                                                                            | :heavy\_check\_mark: | Text to synthesize                                                                                                                                                                                                                                                                                                      | Hello world                                                                                                                                                                                                                 |
| `InputReferences` | \[][components.SpeechInputReference](../../models/components/speechinputreference.mdx)              | :heavy\_minus\_sign: | Reference content for stateless voice cloning: one `input_audio` part carrying the voice sample, optionally accompanied by one `text` part with its transcript. Only routed to endpoints that support voice cloning.                                                                                                    | \[<br />\{<br />"input\_audio": \{<br />"data": "data:audio/wav;base64,UklGRuQXDABXQVZF..."<br />},<br />"type": "input\_audio"<br />},<br />\{<br />"text": "I used to rule the world.",<br />"type": "text"<br />}<br />] |
| `Model`           | `string`                                                                                            | :heavy\_check\_mark: | TTS model identifier                                                                                                                                                                                                                                                                                                    | mistralai/voxtral-mini-tts-2603                                                                                                                                                                                             |
| `Provider`        | [\*components.SpeechRequestProvider](../../models/components/speechrequestprovider.mdx)             | :heavy\_minus\_sign: | Provider-specific passthrough configuration                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                             |
| `ResponseFormat`  | [\*components.SpeechRequestResponseFormat](../../models/components/speechrequestresponseformat.mdx) | :heavy\_minus\_sign: | Audio output format                                                                                                                                                                                                                                                                                                     | pcm                                                                                                                                                                                                                         |
| `SessionID`       | `*string`                                                                                           | :heavy\_minus\_sign: | A unique identifier for grouping related requests (e.g., a conversation or agent workflow). Used for observability grouping in Broadcast and private logging; never sent to the provider. If provided in both the request body and the x-session-id header, the body value takes precedence. Maximum of 256 characters. | session-1234                                                                                                                                                                                                                |
| `Speed`           | `*float64`                                                                                          | :heavy\_minus\_sign: | Playback speed multiplier. Only used by models that support it (e.g. OpenAI TTS). Ignored by other providers.                                                                                                                                                                                                           | 1                                                                                                                                                                                                                           |
| `Trace`           | [\*components.TraceConfig](../../models/components/traceconfig.mdx)                                 | :heavy\_minus\_sign: | Metadata for observability and tracing. Known keys (trace\_id, trace\_name, span\_name, generation\_name, parent\_span\_id) have special handling. Additional keys are passed through as custom metadata to configured broadcast destinations.                                                                          | \{<br />"trace\_id": "trace-abc123",<br />"trace\_name": "my-app-trace"<br />}                                                                                                                                              |
| `User`            | `*string`                                                                                           | :heavy\_minus\_sign: | A unique identifier representing your end-user. Forwarded to Broadcast and private logging as the end-user id; never sent to the provider.                                                                                                                                                                              | user-1234                                                                                                                                                                                                                   |
| `Voice`           | `*string`                                                                                           | :heavy\_minus\_sign: | Voice identifier (provider-specific).                                                                                                                                                                                                                                                                                   | en\_paul\_neutral                                                                                                                                                                                                           |