> ## Documentation Index > Fetch the complete documentation index at: https://docs.gc.ai/llms.txt > Use this file to discover all available pages before exploring further. # Initiate a Chunked Upload > Start a multipart upload session for a large file. Validates the file type, size, and destination up front, then returns an `upload_id`. Send the file in parts with `PUT /files/uploads/{upload_id}/parts/{part_number}`, then finalize with `POST /files/uploads/{upload_id}/complete`. Use this instead of `POST /files` when a single request is impractical (large files, or clients with per-request payload limits). The destination options (`folder_id` / `project_id` / `scope`) behave exactly as on `POST /files`. ## OpenAPI ````yaml POST /files/uploads openapi: 3.0.3 info: title: GC AI External API version: 1.0.0 description: >- The GC AI External API allows programmatic access to GC AI's chat capabilities. It's designed for integration with workflow automation tools like Zapier, Make, n8n, or custom applications. ## Authentication All API requests must include an API key in the `Authorization` header: ``` Authorization: gcai_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ``` API keys can be created in the GC AI app under **Settings → API**. ## Multi-turn Conversations Conversations can span multiple turns: pass the `chat_id` returned by a completion back on your next request to continue the same chat. See [Multi-turn Conversations](/api-reference/concepts/multi-turn). ## Current Limitations The following is not yet available via API: - **Interactive clarification**: the model cannot pause to ask the caller a follow-up question; the `askUserQuestions` tool is disabled on the API surface in beta ## Usage Usage is tracked and viewable in the GC AI app under **Settings → API → View Usage**. ## Support For API support, contact [support@gc.ai](mailto:support@gc.ai) or reach out to your account representative. contact: email: support@gc.ai servers: - url: https://app.gc.ai/api/external/v1 description: Production server security: [] tags: - name: Chat description: AI chat completion endpoints - name: Files description: File upload and management endpoints - name: Folders description: Folder management endpoints - name: Playbooks description: Playbook review endpoints - name: Profiles description: Personal and company profile endpoints - name: Projects description: Project management endpoints - name: Skills description: Skill library management endpoints - name: Utility description: Health check and connectivity endpoints - name: Usage description: Usage and credit/billing reporting endpoints paths: /files/uploads: post: tags: - Files summary: Initiate a chunked upload description: >- Start a multipart upload session for a large file. Validates the file type, size, and destination up front, then returns an `upload_id`. Send the file in parts with `PUT /files/uploads/{upload_id}/parts/{part_number}`, then finalize with `POST /files/uploads/{upload_id}/complete`. Use this instead of `POST /files` when a single request is impractical (large files, or clients with per-request payload limits). The destination options (`folder_id` / `project_id` / `scope`) behave exactly as on `POST /files`. operationId: initiateUpload requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/InitiateUploadRequest' responses: '200': description: Upload session created content: application/json: schema: $ref: '#/components/schemas/InitiateUploadResponse' '400': description: >- Invalid request (unsupported file type, size over the limit, conflicting destination options) content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: Missing or malformed API key content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: Insufficient project access content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: Folder or project not found content: application/json: schema: $ref: '#/components/schemas/Error' '429': description: >- Rate limit exceeded. See [Rate Limits](/api-reference/concepts/rate-limits) for the tiers, limits, and how to back off. headers: Retry-After: schema: type: string description: Seconds to wait before retrying after a rate-limit block. example: '60' required: true description: Seconds to wait before retrying after a rate-limit block. RateLimit-Limit: schema: type: string description: Request quota for the applicable window. example: '3' required: true description: Request quota for the applicable window. RateLimit-Remaining: schema: type: string description: Requests remaining in the current window. example: '0' required: true description: Requests remaining in the current window. RateLimit-Reset: schema: type: string description: Seconds until the quota resets. example: '60' required: true description: Seconds until the quota resets. content: application/json: schema: $ref: '#/components/schemas/Error' '500': description: Internal server error content: application/json: schema: $ref: '#/components/schemas/Error' '503': description: Service temporarily unavailable headers: Retry-After: schema: type: string description: >- Seconds to wait before retrying after a transient service outage. example: '5' required: true description: >- Seconds to wait before retrying after a transient service outage. content: application/json: schema: $ref: '#/components/schemas/Error' security: - ApiKeyAuth: [] components: schemas: InitiateUploadRequest: type: object properties: file_name: type: string minLength: 1 maxLength: 255 description: Original filename, including extension. example: msa-2026.pdf content_type: type: string description: >- MIME type of the file. When omitted, it is derived from the filename extension. example: application/pdf size: type: integer minimum: 0 exclusiveMinimum: true description: >- Total size of the complete file in bytes. Validated up front against the file-size limit so oversized uploads fail before any parts are sent. example: 12582912 folder_id: type: string format: uuid description: >- Target folder ID. Defaults to the user's "My Files" folder. Mutually exclusive with `project_id` and `scope`. project_id: type: string format: uuid description: >- Upload the file into a project. The file is placed in the project's upload folder and linked to the project. Mutually exclusive with `folder_id` and `scope`. scope: type: string enum: - my-files - organization description: >- Upload to the root of a meta-collection ("my-files" or "organization"). Mutually exclusive with `folder_id` and `project_id`. User-scoped keys only. example: my-files required: - file_name - size InitiateUploadResponse: type: object properties: upload_id: type: string format: uuid description: >- Opaque identifier for this upload session. Use it in the part and complete requests. part_size: type: number description: >- Recommended part size in bytes. Split the file into parts no larger than this for reliable transfers. max_parts: type: number description: >- Maximum number of parts allowed for this session. Part numbers run from 1 to this value. expires_at: type: string description: >- ISO 8601 timestamp after which the session expires. Upload all parts and call complete before this. required: - upload_id - part_size - max_parts - expires_at Error: type: object properties: error: type: string description: Error message code: type: string description: >- Machine-readable error code present on some errors (e.g. `RATE_LIMITED`, `INSUFFICIENT_CREDITS`, `TRIAL_NOT_STARTED`, `BILLING_NOT_CONFIGURED`). Branch on this rather than the human-readable `error` string. message: type: string description: Additional error details details: type: object additionalProperties: nullable: true description: Validation error details (for 400 errors) required: - error securitySchemes: ApiKeyAuth: type: apiKey in: header name: Authorization description: |- API key for authentication. Format: `gcai_xxxxxxxxx` Create API keys in the GC AI app under Settings → API. ````