Inworld AI Text To Speech API

openapi: 3.1.0
info:
  title: Inworld Models Text To Speech API
  description: 'List every model available behind the Inworld platform — first-party TTS, STT, and Realtime models plus all third-party LLMs reachable through the LLM Router. Returns provider, model id, capabilities (chat, vision, tool use, speech, streaming), and pricing tier metadata for runtime discovery.

    '
  version: v1
  contact:
    name: Inworld Support
    url: https://docs.inworld.ai/tts/resources/support
  license:
    name: Inworld Terms of Service
    url: https://inworld.ai/legal/terms-of-service
servers:
- url: https://api.inworld.ai
  description: Inworld Production API
security:
- BasicAuth: []
tags:
- name: Text To Speech
  description: Synthesize speech from text using Inworld voice models.
paths:
  /tts/v1/voice:
    post:
      summary: Synthesize Speech
      description: 'Synthesize a single audio response from text. Returns base64-encoded audio plus optional word/character/phoneme alignment metadata. Maximum 2,000 input characters per request and 16 MB output audio.

        '
      operationId: synthesizeSpeech
      tags:
      - Text To Speech
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SynthesizeRequest'
            examples:
              Default:
                $ref: '#/components/examples/SynthesizeExample'
      responses:
        '200':
          description: Synthesized audio returned successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SynthesizeResponse'
        4XX:
          $ref: '#/components/responses/ErrorResponse'
  /tts/v1/voice:stream:
    post:
      summary: Stream Synthesize Speech
      description: 'Stream synthesis. The response is a chunked sequence of JSON envelopes, each containing a base64 audio fragment. Use for low-latency playback of long-form text.

        '
      operationId: streamSynthesizeSpeech
      tags:
      - Text To Speech
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SynthesizeRequest'
      responses:
        '200':
          description: Streamed audio chunks.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SynthesizeStreamChunk'
        4XX:
          $ref: '#/components/responses/ErrorResponse'
  /tts/v1/voice:websocket:
    get:
      summary: WebSocket Synthesize Speech
      description: 'Upgrade to a WebSocket connection for bidirectional streaming synthesis. Clients send `SynthesizeRequest` frames and receive chunked audio frames with timestamp metadata. Auth via `Authorization: Basic` header on the upgrade request.

        '
      operationId: websocketSynthesizeSpeech
      tags:
      - Text To Speech
      responses:
        '101':
          description: Switching protocols to WebSocket.
  /tts/v1/voices:
    get:
      summary: List TTS Voices
      description: 'List voices available for synthesis. Includes Inworld-shipped voices and any custom-cloned or designed voices in the caller''s workspace.

        '
      operationId: listTtsVoices
      tags:
      - Text To Speech
      parameters:
      - name: filter
        in: query
        required: false
        description: Optional filter expression (e.g. by tag, language, gender).
        schema:
          type: string
      responses:
        '200':
          description: Voices returned successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ListVoicesResponse'
        4XX:
          $ref: '#/components/responses/ErrorResponse'
components:
  schemas:
    PhoneticDetail:
      type: object
      properties:
        wordIndex:
          type: integer
        phones:
          type: array
          items:
            type: object
            properties:
              phoneSymbol:
                type: string
                description: IPA phone symbol.
              startTimeSeconds:
                type: number
              durationSeconds:
                type: number
              visemeSymbol:
                type: string
                description: Viseme label for lipsync.
        isPartial:
          type: boolean
    AudioConfig:
      type: object
      required:
      - audioEncoding
      properties:
        audioEncoding:
          type: string
          enum:
          - LINEAR16
          - MP3
          - OGG_OPUS
          - ALAW
          - MULAW
          - FLAC
          - PCM
          - WAV
        sampleRateHertz:
          type: integer
          minimum: 8000
          maximum: 48000
          default: 48000
        bitRate:
          type: integer
          default: 128000
          description: Bits per second. Compressed formats only.
        speakingRate:
          type: number
          minimum: 0.5
          maximum: 1.5
          default: 1.0
    SynthesisUsage:
      type: object
      properties:
        processedCharactersCount:
          type: integer
        modelId:
          type: string
    SynthesizeStreamChunk:
      type: object
      properties:
        audioContent:
          type: string
          format: byte
        timestampInfo:
          $ref: '#/components/schemas/TimestampInfo'
        usage:
          $ref: '#/components/schemas/SynthesisUsage'
    TimestampInfo:
      type: object
      properties:
        wordAlignment:
          $ref: '#/components/schemas/WordAlignment'
        characterAlignment:
          $ref: '#/components/schemas/CharacterAlignment'
    WordAlignment:
      type: object
      properties:
        words:
          type: array
          items:
            type: string
        wordStartTimeSeconds:
          type: array
          items:
            type: number
        wordEndTimeSeconds:
          type: array
          items:
            type: number
        phoneticDetails:
          type: array
          items:
            $ref: '#/components/schemas/PhoneticDetail'
    SynthesizeResponse:
      type: object
      properties:
        audioContent:
          type: string
          format: byte
          description: Base64-encoded audio bytes.
        usage:
          $ref: '#/components/schemas/SynthesisUsage'
        timestampInfo:
          $ref: '#/components/schemas/TimestampInfo'
    Error:
      type: object
      properties:
        code:
          type: integer
        message:
          type: string
        details:
          type: array
          items:
            type: object
    ListVoicesResponse:
      type: object
      properties:
        voices:
          type: array
          items:
            $ref: '#/components/schemas/Voice'
    CharacterAlignment:
      type: object
      properties:
        characters:
          type: array
          items:
            type: string
        characterStartTimeSeconds:
          type: array
          items:
            type: number
        characterEndTimeSeconds:
          type: array
          items:
            type: number
    Voice:
      type: object
      properties:
        voiceId:
          type: string
        displayName:
          type: string
        languages:
          type: array
          items:
            type: string
        gender:
          type: string
        tags:
          type: array
          items:
            type: string
        source:
          type: string
          enum:
          - INWORLD
          - IVC
          - DESIGN
    SynthesizeRequest:
      type: object
      required:
      - text
      - voiceId
      - modelId
      - audioConfig
      properties:
        text:
          type: string
          maxLength: 2000
          description: Text to synthesize. Maximum 2,000 characters per request.
        voiceId:
          type: string
          description: Voice identifier (shipped voice name or custom voice id).
        modelId:
          type: string
          description: Inworld TTS model id.
          enum:
          - inworld-tts-2
          - inworld-tts-1.5-max
          - inworld-tts-1.5-mini
        audioConfig:
          $ref: '#/components/schemas/AudioConfig'
        language:
          type: string
          description: BCP-47 language tag (e.g. `en-US`).
        deliveryMode:
          type: string
          description: TTS-2 only. Controls stability vs. expressiveness.
          enum:
          - STABLE
          - BALANCED
          - CREATIVE
          default: BALANCED
        temperature:
          type: number
          minimum: 0
          maximum: 2
          default: 1.0
          description: Randomness. Ignored on TTS-2.
        timestampType:
          type: string
          enum:
          - WORD
          - CHARACTER
          description: If set, return alignment metadata of the requested granularity.
        applyTextNormalization:
          type: string
          enum:
          - true
          - false
          description: Normalize numbers, dates, abbreviations, etc. before synthesis.
  responses:
    ErrorResponse:
      description: Error response.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  examples:
    SynthesizeExample:
      summary: Basic synthesis with LINEAR16
      value:
        text: Hello, world! What a wonderful day to be a text-to-speech model.
        voiceId: Dennis
        modelId: inworld-tts-2
        audioConfig:
          audioEncoding: LINEAR16
          sampleRateHertz: 22050
        deliveryMode: BALANCED
        applyTextNormalization: true
  securitySchemes:
    BasicAuth:
      type: http
      scheme: basic