> ## Documentation Index > Fetch the complete documentation index at: https://docs.voice.wixzel.com/llms.txt > Use this file to discover all available pages before exploring further. # Retrieve a knowledge base file > Poll this until `status` is `ready` or `failed`. Requires `knowledge_bases:read`. ## OpenAPI ````yaml /openapi.json get /v1/knowledge-bases/{id}/files/{fileId} openapi: 3.1.0 info: title: Wixzel Voice API version: '2026-09-01' description: >- APIs for agentic telephony. One API key, one balance, every voice engine. ## Authentication Send your key as `Authorization: Bearer wv_live_...`. Keys are scoped: grant only what an integration needs. There is no admin scope. ## Versioning The `/v1` prefix covers additive changes. Behavioural changes ship behind a dated `Wixzel-Version` header, and existing keys keep the behaviour they were created with. ## Money Amounts are integer **micro-USD** (1,000,000 = $1.00). Voice usage is billed per second, per token and per character, so a float dollar figure cannot represent it without disagreeing with the ledger. ## Errors Every error carries a stable `code` and a `request_id`. Match on `code`; the `message` is for humans and may change. contact: name: Wixzel Voice url: https://voice.wixzel.com servers: - url: https://api.voice.wixzel.com description: Production security: [] tags: - name: Calls description: Place calls and read what happened on them. - name: Realtime description: Talk to an agent from a browser or app, with no phone line. - name: Agents description: >- The prompt, voice and behaviour of a caller, and its mascot: the animated face people see on your share link, your website and in your apps. - name: Leads description: People to call, and data to merge into prompts. - name: Campaigns description: Call a list of leads with one agent. - name: Knowledge bases description: Facts an agent can draw on mid-call. - name: Phone numbers description: Numbers on your SIP trunks. - name: SIP trunks description: Your carrier connections. - name: Appointments description: Bookings, including ones agents make on calls. - name: Usage description: Itemised billing lines. - name: Billing description: Balance, ledger and top-ups. - name: API keys description: Create, scope and rotate keys. - name: Engines description: What the platform can serve, and what it costs. - name: Voices description: Cloned voices, made from your own recordings, for your agents to speak in. - name: Callers description: Who called your agents, where from and on what, and the blocklist. - name: Webhooks description: Where events are sent, and what happened when they got there. - name: MCP servers description: Other apps’ tools, for agents to use while they are on a call. - name: Tools description: >- Your own tools, for agents to use while they are on a call: a webhook to your server, or an action in the caller’s app. - name: WhatsApp description: >- WhatsApp business numbers, the agents that answer their chats, and messages agents send. - name: Meetings description: >- Agents in Zoom, Google Meet and Teams meetings, through your own Attendee account. paths: /v1/knowledge-bases/{id}/files/{fileId}: get: tags: - Knowledge bases summary: Retrieve a knowledge base file description: >- Poll this until `status` is `ready` or `failed`. Requires `knowledge_bases:read`. parameters: - schema: type: string pattern: ^[0-9a-f]{24}$ example: 6a96a3ead6e886d42462dd3e required: true name: id in: path - schema: type: string pattern: ^[0-9a-f]{24}$ example: 6a96a3ead6e886d42462dd3e required: true name: fileId in: path responses: '200': description: The file content: application/json: schema: $ref: '#/components/schemas/KnowledgeFile' '400': description: Invalid request content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: Missing or invalid API key content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: Key lacks the required scope content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: No such record content: application/json: schema: $ref: '#/components/schemas/Error' '429': description: Rate limited. Retry after the interval in `Retry-After`. content: application/json: schema: $ref: '#/components/schemas/Error' security: - bearerAuth: [] components: schemas: KnowledgeFile: type: object properties: id: type: string pattern: ^[0-9a-f]{24}$ example: 6a96a3ead6e886d42462dd3e object: type: string enum: - knowledge_file knowledge_base_id: type: string pattern: ^[0-9a-f]{24}$ example: 6a96a3ead6e886d42462dd3e name: type: string kind: type: string enum: - pdf - docx - txt - md - csv - html - image - video description: >- `image` and `video` are for agents to send on WhatsApp; they are found by their `description`. bytes: type: integer pages: type: - integer - 'null' chars: type: integer description: Characters of text read from it. chunks: type: integer description: Passages the agent can search. status: type: string enum: - processing - ready - failed description: >- `processing` while it is read (usually seconds); `ready` once agents can search it; `failed` with `error` saying why. error: type: - string - 'null' description: >- Why it failed, or a note on a ready file (such as only part of it being kept). source_url: type: - string - 'null' description: type: string description: What the file is or shows. Required for images and videos. mime_type: type: - string - 'null' sendable: type: boolean description: >- Whether agents can send it on WhatsApp: its original was kept. Files added before WhatsApp sending was available are not. created_at: type: string format: date-time description: ISO 8601, always UTC. example: '2026-09-01T12:00:00.000Z' required: - id - object - knowledge_base_id - name - kind - bytes - pages - chars - chunks - status - error - source_url - description - mime_type - sendable - created_at description: >- A file in a knowledge base. A document’s text is read and split into passages; an agent using the knowledge base searches them during a call with the built-in `search_knowledge` tool. An image or video is found by its `description`. The original is kept so agents can send it on WhatsApp. Error: type: object properties: error: type: object properties: type: type: string enum: - invalid_request_error - authentication_error - permission_error - rate_limit_error - insufficient_credits - not_found_error - conflict_error - api_error code: type: string description: Stable machine-readable code. example: agent_not_found message: type: string description: >- Human-readable explanation. Do not match on this — match on code. param: type: string description: Which field caused the failure, when applicable. doc_url: type: string request_id: type: string description: Quote this when asking for help. example: req_01HXYZ... required: - type - code - message - request_id required: - error securitySchemes: bearerAuth: type: http scheme: bearer description: >- Your Wixzel Voice API key: `Authorization: Bearer wv_live_...`. Keys are scoped; grant only what the integration needs. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.