Cartesia Text-to-Speech API

openapi: 3.0.3
info:
  title: Cartesia Agents Text-to-Speech API
  description: 'The Cartesia REST API for real-time voice AI - text-to-speech and voice-changer generation (single-shot bytes or Server-Sent Events), batch speech-to-text transcription, voice management and cloning, audio infill, custom datasets, pronunciation dictionaries, API keys and scoped access tokens, the Voice Agents platform (agents, calls, call batches, phone numbers, telephony providers, webhooks, deployments, knowledge base documents/folders, and evaluation metrics), and usage reporting. All requests require a `Cartesia-Version` header and an `Authorization: Bearer` API key (`sk_car_...`) or short-lived access token. The lowest-latency, streaming surface for TTS and STT is a separate WebSocket protocol documented in the companion AsyncAPI document at asyncapi/cartesia-ai-asyncapi.yml.'
  version: '2026-03-01'
  contact:
    name: Cartesia
    url: https://cartesia.ai
  license:
    name: API documentation - Cartesia Terms of Service
    url: https://cartesia.ai/terms-of-service
servers:
- url: https://api.cartesia.ai
  description: Cartesia production API
security:
- bearerAuth: []
tags:
- name: Text-to-Speech
  description: Single-shot and streamed speech generation over plain HTTP.
paths:
  /tts/bytes:
    post:
      operationId: ttsBytes
      tags:
      - Text-to-Speech
      summary: Text-to-Speech (Bytes)
      description: Synthesizes a complete transcript and returns raw audio bytes in a single response.
      parameters:
      - $ref: '#/components/parameters/CartesiaVersion'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/TtsRequest'
      responses:
        '200':
          description: Synthesized audio.
          content:
            audio/*:
              schema:
                type: string
                format: binary
        '401':
          $ref: '#/components/responses/Unauthorized'
        '422':
          $ref: '#/components/responses/ValidationError'
  /tts/sse:
    post:
      operationId: ttsSse
      tags:
      - Text-to-Speech
      summary: Text-to-Speech (SSE)
      description: Streams audio chunks with extra metadata (timestamps) from a complete transcript as Server-Sent Events.
      parameters:
      - $ref: '#/components/parameters/CartesiaVersion'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/TtsRequest'
      responses:
        '200':
          description: Server-Sent Events stream of audio chunks and metadata.
          content:
            text/event-stream:
              schema:
                type: string
        '401':
          $ref: '#/components/responses/Unauthorized'
        '422':
          $ref: '#/components/responses/ValidationError'
components:
  schemas:
    OutputFormat:
      type: object
      required:
      - container
      - sample_rate
      properties:
        container:
          type: string
          enum:
          - raw
          - wav
          - mp3
        encoding:
          type: string
          enum:
          - pcm_f32le
          - pcm_s16le
          - pcm_mulaw
          - pcm_alaw
          description: Required for raw and wav containers.
        sample_rate:
          type: integer
          enum:
          - 8000
          - 16000
          - 22050
          - 24000
          - 44100
          - 48000
        bit_rate:
          type: integer
          enum:
          - 32000
          - 64000
          - 96000
          - 128000
          - 192000
          description: Required for mp3 container.
    GenerationConfig:
      type: object
      properties:
        volume:
          type: number
          minimum: 0.5
          maximum: 2.0
          default: 1
        speed:
          type: number
          minimum: 0.6
          maximum: 1.5
          default: 1
        emotion:
          type: string
          enum:
          - neutral
          - happy
          - excited
          - calm
          - angry
          - content
          - sad
          - scared
          - proud
          - confident
          - distant
          - skeptical
          - contemplative
          - determined
    TtsRequest:
      type: object
      required:
      - model_id
      - transcript
      - voice
      - output_format
      properties:
        model_id:
          type: string
          enum:
          - sonic-3.5
          - sonic-3
          - sonic-latest
        transcript:
          type: string
        voice:
          $ref: '#/components/schemas/VoiceRef'
        language:
          type: string
          description: One of 40+ supported language codes (en, fr, de, es, ja, zh, ...).
        output_format:
          $ref: '#/components/schemas/OutputFormat'
        pronunciation_dict_id:
          type: string
          nullable: true
        generation_config:
          $ref: '#/components/schemas/GenerationConfig'
    Error:
      type: object
      properties:
        title:
          type: string
        message:
          type: string
        error_code:
          type: string
        status_code:
          type: integer
        doc_url:
          type: string
        request_id:
          type: string
    VoiceRef:
      type: object
      required:
      - mode
      - id
      properties:
        mode:
          type: string
          enum:
          - id
        id:
          type: string
          format: uuid
  responses:
    Unauthorized:
      description: Missing, invalid, or expired API key / access token.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    ValidationError:
      description: The request payload failed validation.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  parameters:
    CartesiaVersion:
      name: Cartesia-Version
      in: header
      required: true
      description: API version date, e.g. 2026-03-01.
      schema:
        type: string
        example: '2026-03-01'
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: sk_car_... API key or short-lived access token
      description: 'Cartesia API key (sk_car_...) or a short-lived access token minted via POST /access-token, passed as Authorization: Bearer <token>. Every request also requires the Cartesia-Version header.'