> ## Documentation Index > Fetch the complete documentation index at: https://heygen-1fa696a7.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Create Speech Input Token > Create a single-use token that authenticates one WebSocket handshake to `/v3/models/audio/tts/stream-input` or `/v3/models/audio/tts/multi-stream-input` as the caller. Use it for a client that cannot set headers, such as a browser: your backend creates the token with its API key, and the client connects with `?token=`. The token is valid until `expires_at`: 15 minutes, or less when the API key or OAuth access token expires sooner. The first accepted handshake uses it. A handshake refused for a bad parameter does not use it. A key with no time left gets HTTP 401. The response has `Cache-Control: no-store`. ## OpenAPI ````yaml /openapi/external-api.json post /v3/models/audio/tts/stream-input/tokens openapi: 3.1.0 info: title: HeyGen External API version: 1.0.0 description: >- HeyGen's external API for programmatic AI video creation. See https://docs.heygen.com for full documentation. contact: name: HeyGen Product Infra url: https://heygen.com servers: - url: https://api.heygen.com description: Production security: - ApiKeyAuth: [] - BearerAuth: [] tags: - name: Video Agent description: Create videos from text prompts using AI - name: Videos description: Create, list, retrieve, and delete videos - name: Templates description: Generate videos from reusable templates by replacing their variables - name: Voices description: Text-to-speech and voice management - name: Audio description: Search the background-music and sound-effects catalog - name: Video Translate description: Translate videos into other languages - name: AI Clipping description: Turn long-form videos into ready-to-share short clips with captions - name: Batches description: Create and track batches of videos. - name: Video Translation Batches description: Create and track batches of video translations. - name: Lipsync Batches description: Create and track batches of lipsyncs. - name: Asset Batches description: Create and track batches of direct-to-S3 asset uploads. - name: User description: Account information and billing - name: API Keys description: Inspect the API key authenticating the current request - name: Avatars description: List and manage avatars and looks - name: Assets description: Upload files for use in video creation - name: Folders description: >- Create folders to organize videos and translations in the workspace, and look up any folder, Assets library folders included, by id - name: Webhooks description: Manage webhook endpoints and events - name: Lipsync description: Dub or replace audio on existing videos - name: Brand description: >- Brand-related resources — brand kits (colors, fonts, logos) and brand glossaries (custom term translations) - name: HyperFrames description: Render HyperFrames composition zips into video — separate from /v3/videos - name: Models description: '' - name: Filler Word Removal description: '' paths: /v3/models/audio/tts/stream-input/tokens: post: tags: - Models summary: Create Speech Input Token description: >- Create a single-use token that authenticates one WebSocket handshake to `/v3/models/audio/tts/stream-input` or `/v3/models/audio/tts/multi-stream-input` as the caller. Use it for a client that cannot set headers, such as a browser: your backend creates the token with its API key, and the client connects with `?token=`. The token is valid until `expires_at`: 15 minutes, or less when the API key or OAuth access token expires sooner. The first accepted handshake uses it. A handshake refused for a bad parameter does not use it. A key with no time left gets HTTP 401. The response has `Cache-Control: no-store`. operationId: createModelSpeechInputToken responses: '200': description: Successful response content: application/json: schema: type: object properties: data: $ref: '#/components/schemas/SpeechInputTokenData' '400': description: Invalid request parameters content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' '401': description: Authentication failed content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: unauthorized message: Invalid or expired API key. Verify your x-api-key header. param: null doc_url: null '403': description: Forbidden content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: insufficient_api_key_scope message: The API key's policy lacks `voices:write`. param: null doc_url: null '429': description: Rate limit exceeded content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: rate_limit_exceeded message: >- Too many requests. Retry after the duration specified in the Retry-After header. param: null doc_url: null headers: Retry-After: description: Seconds to wait before retrying schema: type: integer security: - ApiKeyAuth: [] - BearerAuth: [] components: schemas: SpeechInputTokenData: properties: token: description: >- Single-use credential for one input-streaming handshake, sent as `?token=`. title: Token type: string expires_at: description: When the token stops being accepted, if it has not been used. format: date-time title: Expires At type: string expires_in: description: Seconds until `expires_at`. title: Expires In type: integer required: - token - expires_at - expires_in title: SpeechInputTokenData type: object StandardAPIError: type: object properties: code: type: string description: Machine-readable error code example: invalid_parameter message: type: string description: Human-readable error message example: Video not found param: type: - string - 'null' description: Which request field caused the error doc_url: type: - string - 'null' description: Link to error documentation errors: type: array description: >- Per-item error details for batch/multi-node failures (e.g. graph compilation errors by node). items: $ref: '#/components/schemas/StandardAPIErrorDetail' request_id: type: string description: >- Request identifier, also returned in the X-HeyGen-Request-Id response header. Include it when contacting support. example: 8c4f0b9e1d2a4f6b9e3c7a1d5f2b8e40 required: - code - message StandardAPIErrorDetail: type: object properties: code: type: string description: Machine-readable error code example: unknown_node_type message: type: string description: Human-readable error message example: Unknown node type node_id: type: string description: Graph node id this error pertains to, if applicable port: type: string description: Port name on the node this error pertains to, if applicable path: type: string description: Field path within the item this error pertains to, if applicable required: - code - message securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key description: HeyGen API key. Obtain from your HeyGen dashboard. BearerAuth: type: http scheme: bearer description: OAuth2 bearer token. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.