> ## Documentation Index > Fetch the complete documentation index at: https://slng.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Fish Audio TTS S2.1 Pro > Synthesize speech with Fish Speech S2.1 Pro over one-shot HTTP. Returns binary audio in the requested format. MessagePack requests may include inline reference audio for voice cloning. 3rd Party API Hosted by Fish Audio For SLNG Sovereign Hosting in any of our 11 regions [contact us](mailto:support@slng.ai). ## OpenAPI ````yaml POST /v1/tts/fish/tts:s2.1-pro openapi: 3.0.3 info: title: SLNG Gateway API - Fish Audio TTS version: 0.1.0 description: Unified API for speech-to-text and text-to-speech services. contact: name: SLNG Support email: support@slng.ai servers: - url: https://api.slng.ai description: Production - url: https://stageapi.slng.ai description: Staging security: - BearerAuth: [] tags: - name: Fish Audio TTS S2 Pro description: Fish Audio TTS S2 Pro over one-shot HTTP and MessagePack WebSocket. - name: Fish Audio TTS S2.1 Pro description: Fish Audio TTS S2.1 Pro over one-shot HTTP and MessagePack WebSocket. - name: Fish Audio TTS Stream description: >- Fish Audio HTTP streaming TTS with SSE audio chunks and timestamp alignments. paths: /v1/tts/fish/tts:s2.1-pro: post: tags: - Fish Audio TTS S2.1 Pro summary: Fish Audio TTS S2.1 Pro description: >- Synthesize speech with Fish Speech S2.1 Pro over one-shot HTTP. Returns binary audio in the requested format. MessagePack requests may include inline reference audio for voice cloning. operationId: fish/tts:s2.1-pro parameters: - $ref: '#/components/parameters/XWorldPartFish' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/FishTtsRequest' examples: basic: summary: Basic synthesis value: text: Hello from Fish Audio S2.1 Pro. reference_id: 9a9cf47702da476aa4629e2506d4a857 format: mp3 application/msgpack: schema: $ref: '#/components/schemas/FishTtsRequest' examples: cloning: summary: Synthesis with inline reference audio (MessagePack only) value: text: Hello from Fish Audio S2.1 Pro. format: mp3 responses: '200': $ref: '#/components/responses/FishTtsSynthesisSuccess' '400': $ref: '#/components/responses/ProviderBadRequest' '401': $ref: '#/components/responses/ProviderUnauthorized' '402': $ref: '#/components/responses/ProviderPaymentRequired' '413': $ref: '#/components/responses/ProviderPayloadTooLarge' '415': $ref: '#/components/responses/UnsupportedMediaType' '503': $ref: '#/components/responses/ProviderServiceUnavailable' components: parameters: XWorldPartFish: name: X-World-Part-Override in: header required: false description: Target world part override. Auto-selected if not provided. schema: type: string enum: - us schemas: FishTtsRequest: type: object description: Fish Audio TTS request. Shared by one-shot and streaming synthesis. required: - text properties: text: type: string minLength: 1 description: >- Text to synthesize. S2-family variants support multi-speaker dialogue markers. reference_id: type: string description: >- Fish Audio voice-model ID. For multi-speaker synthesis, provide one ID per speaker as an array. references: type: array description: >- Inline reference audio for voice cloning. MessagePack-only, as the entries carry binary audio. items: $ref: '#/components/schemas/FishTtsReference' prosody: type: object description: Prosody controls. properties: speed: type: number minimum: 0.5 maximum: 2 default: 1 description: Speech speed multiplier. volume: type: number minimum: -20 maximum: 20 default: 0 description: Volume adjustment in dB. normalize_loudness: type: boolean default: true description: Whether to normalize output loudness. temperature: type: number minimum: 0 maximum: 1 default: 0.7 description: Sampling temperature. top_p: type: number minimum: 0 maximum: 1 default: 0.7 description: Nucleus sampling probability mass. chunk_length: type: integer minimum: 100 maximum: 300 default: 300 description: Target chunk length for synthesis. normalize: type: boolean default: true description: Whether to normalize input text before synthesis. format: type: string enum: - wav - pcm - mp3 - opus default: mp3 description: Output audio format. sample_rate: type: integer nullable: true enum: - 8000 - 16000 - 24000 - 32000 - 44100 - 48000 description: >- Output sample rate in Hz. Defaults to the provider default for the chosen format when omitted. mp3_bitrate: type: integer enum: - 64 - 128 - 192 default: 128 description: MP3 bitrate in kbps (used when `format` is `mp3`). opus_bitrate: type: integer enum: - -1000 - 24000 - 32000 - 48000 - 64000 default: -1000 description: >- Opus bitrate in bps (used when `format` is `opus`). `-1000` selects the provider default. latency: type: string enum: - low - normal - balanced default: normal description: Latency/quality trade-off. max_new_tokens: type: integer default: 1024 description: Maximum number of new tokens to generate. repetition_penalty: type: number default: 1.2 description: Penalty applied to repeated tokens. min_chunk_length: type: integer minimum: 0 maximum: 100 default: 50 description: Minimum chunk length for synthesis. condition_on_previous_chunks: type: boolean default: true description: Whether generation is conditioned on previously generated chunks. early_stop_threshold: type: number minimum: 0 maximum: 1 default: 1 description: Early-stop threshold for generation. features: type: array description: Optional feature flags. items: type: string FishTtsReference: type: object description: >- Inline reference audio for voice cloning. Supplied only over `application/msgpack`. required: - audio - text properties: audio: type: string format: binary description: Reference audio bytes (MessagePack binary value). text: type: string description: Transcript of the reference audio. AudioBinary: type: string format: binary description: Binary audio data. ProviderErrorResponse: type: object description: > Provider error response. Contains error information from the upstream provider. Common errors include invalid parameters, unsupported media types, or payloads that exceed limits. properties: error: type: string description: >- Error type or category (e.g., "TTS service error", "Validation error"). example: TTS service error upstream_status: type: integer description: >- Original HTTP status code from the provider (may differ from gateway response code). example: 400 details: type: string description: Detailed error message from the provider. example: 'Fish Audio TTS error: 400 Bad Request - Invalid reference_id' required: - error responses: FishTtsSynthesisSuccess: description: >- Synthesis successful. Returns binary audio in the format requested via `format`. content: audio/*: schema: $ref: '#/components/schemas/AudioBinary' ProviderBadRequest: description: Bad request - invalid parameters provided. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' examples: validation-error: summary: Validation error value: error: Validation error details: 'Missing required field: text' ProviderUnauthorized: description: Invalid or missing API key. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderPaymentRequired: description: Insufficient credit or payment required. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderPayloadTooLarge: description: Request payload exceeds the provider size limit. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' UnsupportedMediaType: description: Unsupported request media type. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' ProviderServiceUnavailable: description: Service unavailable. content: application/json: schema: $ref: '#/components/schemas/ProviderErrorResponse' securitySchemes: BearerAuth: type: http scheme: bearer description: | API key issued by SLNG. Pass as `Authorization: Bearer `. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.