> ## Documentation Index > Fetch the complete documentation index at: https://docs.case.dev/llms.txt > Use this file to discover all available pages before exploring further. # Stream text-to-speech audio > Convert text to speech using ElevenLabs AI voices with streaming for real-time playback. Returns audio data as an MP3 stream for immediate playback with minimal latency. Perfect for legal document narration, client presentations, or accessibility features. ## OpenAPI ````yaml /openapi.json post /voice/v1/speak/stream openapi: 3.1.0 info: title: Case.dev API description: >- The AI-native platform for legal technology. Build smarter legal applications with our suite of AI-powered APIs. version: 1.0.0 contact: name: Case.dev Support email: support@casemark.com url: https://case.dev license: name: Proprietary url: https://case.dev/terms servers: - url: https://api.case.dev description: Production security: - bearerAuth: [] tags: - name: Vaults description: Secure document storage with semantic search and GraphRAG - name: Memory description: >- Persistent memory for AI agents with semantic search and 12 generic indexed tag fields - name: OCR description: Extract text from PDFs, images, and scanned documents - name: Voice description: Audio transcription and text-to-speech - name: LLMs description: Access 40+ language models through a unified API - name: Search description: Web search, AI answers, and deep research - name: Mail description: Managed inboxes for agent email workflows - name: Media description: Transcript retrieval and captioned media clip generation - name: Legal description: Legal research tools including citation verification - name: Privilege description: Privilege detection for e-discovery and litigation workflows - name: Compute description: Serverless GPU and CPU infrastructure - name: Format description: Document formatting and template rendering (MD/JSON to PDF/DOCX) - name: SuperDoc description: Document conversion and template automation - name: Webhooks description: Webhook endpoint management - name: System description: Public system metadata and discovery endpoints - name: Usage description: Usage reporting and webhook subscriptions - name: Database description: Serverless PostgreSQL databases with instant branching - name: Translation description: Language detection and translation for multilingual legal workflows - name: Skills description: Search and read legal AI skills for agents - name: Agents description: >- Create, manage, and execute AI agents with tool access, sandbox environments, and async run workflows - name: Matters description: Matter-native legal workspaces and orchestration primitives - name: Applications Projects description: Web application project management - name: Applications Deployments description: Web application deployment management - name: Applications Domains description: Custom domain configuration for applications - name: Applications Env Vars description: Environment variable management for applications paths: /voice/v1/speak/stream: post: tags: - Voice summary: Stream text-to-speech audio description: >- Convert text to speech using ElevenLabs AI voices with streaming for real-time playback. Returns audio data as an MP3 stream for immediate playback with minimal latency. Perfect for legal document narration, client presentations, or accessibility features. operationId: streamTextToSpeech requestBody: required: true content: application/json: schema: type: object required: - text properties: text: type: string description: Text to convert to speech maxLength: 5000 voice_id: type: string description: >- ElevenLabs voice ID (defaults to Rachel for professional clarity) default: EXAVITQu4vr4xnSDxMaL model_id: type: string description: TTS model to use default: eleven_multilingual_v2 enum: - eleven_monolingual_v1 - eleven_multilingual_v1 - eleven_multilingual_v2 - eleven_turbo_v2 voice_settings: type: object description: >- Optional voice tuning controls for delivery, consistency, and emphasis properties: stability: type: number minimum: 0 maximum: 1 description: Voice stability (0-1) similarity_boost: type: number minimum: 0 maximum: 1 description: Similarity boost (0-1) style: type: number minimum: 0 maximum: 1 description: Style exaggeration (0-1) use_speaker_boost: type: boolean description: Enable speaker boost language_code: type: string description: Language code (e.g., 'en', 'es', 'fr') output_format: type: string description: Audio output format enum: - mp3_44100_128 - mp3_22050_32 - pcm_16000 - pcm_22050 - pcm_24000 - pcm_44100 default: mp3_44100_128 optimize_streaming_latency: type: integer description: Optimize for streaming latency (0-4) minimum: 0 maximum: 4 seed: type: integer description: Random seed for reproducible generation previous_text: type: string description: Previous text for context next_text: type: string description: Next text for context apply_text_normalization: type: boolean description: Apply text normalization default: true enable_logging: type: boolean description: Enable request logging default: true responses: '200': description: Audio stream successfully generated content: audio/mpeg: schema: type: string format: binary description: MP3 audio stream headers: Content-Type: description: Audio MIME type schema: type: string example: audio/mpeg Transfer-Encoding: description: Chunked encoding for streaming schema: type: string example: chunked '400': description: Invalid request parameters content: application/json: schema: type: object properties: message: type: string example: text is required '401': description: Authentication failed content: application/json: schema: type: object properties: message: type: string example: Invalid API key data: type: object properties: code: type: string example: AUTH_INVALID '403': description: Insufficient permissions content: application/json: schema: type: object properties: message: type: string example: API key does not have access to voice/TTS service data: type: object properties: code: type: string example: PERMISSION_DENIED components: securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: API Key description: API key starting with `sk_case_` ````