> ## Documentation Index > Fetch the complete documentation index at: https://docs.nineninesix.ai/llms.txt > Use this file to discover all available pages before exploring further. # Text-to-Speech (Bytes) > Generate audio from text and return the **complete audio file in a single response** — the body is the raw audio in the requested format. Use this when you want the whole clip at once; for incremental low-latency playback use `/tts/sse` or the WebSocket endpoint instead. The `wav` container is available on this endpoint only. ## OpenAPI ````yaml api-reference/openapi.json POST /tts/bytes openapi: 3.1.0 info: title: Nineninesix TTS API description: >- Cartesia-compatible Text-to-Speech API for voice agents and real-time dialogue. Point the official Cartesia SDKs at this base URL and they just work. version: 0.3.0 contact: name: Nineninesix Support email: ulan@nineninesix.ai servers: - url: https://api.nineninesix.ai description: Production security: - bearerAuth: [] - apiKeyHeader: [] tags: - name: Speech description: Generate audio from text. - name: Voices description: List, fetch, and clone voices. paths: /tts/bytes: post: tags: - Speech summary: Text-to-Speech (Bytes) description: >- Generate audio from text and return the **complete audio file in a single response** — the body is the raw audio in the requested format. Use this when you want the whole clip at once; for incremental low-latency playback use `/tts/sse` or the WebSocket endpoint instead. The `wav` container is available on this endpoint only. operationId: createSpeechBytes requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/TTSRequest' examples: wav: summary: WAV (PCM) at 22050 Hz value: model_id: gepard-1.0 transcript: Today is a wonderful day to build something people love! voice: mode: id id: a0e99841-438c-4a64-b679-ae501e7d6091 output_format: container: wav encoding: pcm_s16le sample_rate: 22050 telephony: summary: 8 kHz μ-law for Twilio/SIP value: model_id: gepard-1.0 transcript: Thanks for calling. How can I help? voice: mode: id id: a0e99841-438c-4a64-b679-ae501e7d6091 output_format: container: raw encoding: pcm_mulaw sample_rate: 8000 responses: '200': description: >- The audio file in the requested format. A `wav` container is returned as `Content-Type: audio/wav` (the playground renders an audio player); a `raw` container is returned as `application/octet-stream` (raw PCM has no header and won't play in a browser). content: audio/wav: schema: type: string format: binary application/octet-stream: schema: type: string format: binary '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '429': $ref: '#/components/responses/RateLimited' '502': $ref: '#/components/responses/UpstreamUnavailable' components: schemas: TTSRequest: type: object required: - model_id - transcript - voice - output_format properties: model_id: type: string enum: - gepard-1.0 description: The TTS model. Currently `gepard-1.0`. transcript: type: string description: The text to synthesize. Billed at 1 credit per character. voice: $ref: '#/components/schemas/VoiceSpecifier' output_format: $ref: '#/components/schemas/OutputFormat' language: type: string description: Optional language code (e.g. `en`). example: en VoiceSpecifier: type: object required: - mode - id properties: mode: type: string enum: - id description: Voice selection mode. id: type: string description: The voice ID. example: a0e99841-438c-4a64-b679-ae501e7d6091 OutputFormat: type: object description: >- Output audio format. Each field is validated against a fixed set; anything outside these values returns 400 with no silent fallback. required: - container - encoding - sample_rate properties: container: type: string enum: - raw - wav description: >- `wav` is available on `/tts/bytes` only; streaming endpoints are `raw`-only. encoding: type: string enum: - pcm_s16le - pcm_mulaw - pcm_alaw description: '`pcm_mulaw`/`pcm_alaw` are 8-bit G.711 telephony codecs.' sample_rate: type: integer enum: - 8000 - 16000 - 22050 description: >- The model is natively 22050 Hz; 8000/16000 are resampled server-side. Error: type: object properties: error: type: string description: Machine-readable error code. example: payment_required message: type: string description: Human-readable description. example: insufficient credits responses: BadRequest: description: >- Malformed request or unsupported `output_format` (bad container, encoding, or sample rate). content: application/json: schema: $ref: '#/components/schemas/Error' example: error: invalid_output_format message: unsupported sample_rate Unauthorized: description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: unauthorized message: invalid API key PaymentRequired: description: Insufficient credits. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: payment_required message: insufficient credits RateLimited: description: >- Per-org rate or concurrency limit reached. Honor the `Retry-After` header. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: rate_limited message: requests/min limit exceeded for your tier UpstreamUnavailable: description: The synthesis backend errored. Any pre-charge is refunded automatically. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: upstream_unavailable message: synthesis backend error securitySchemes: bearerAuth: type: http scheme: bearer description: 'Pass your API key as a Bearer token: `Authorization: Bearer sk_996_...`.' apiKeyHeader: type: apiKey in: header name: X-API-Key description: Alternatively, pass your API key in the `X-API-Key` header. ````