> ## 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. # Attach a File to a Project > Attach an already-uploaded file to a project. The file remains in its current folder; this only records the project link. Requires write access to the project and read access to the file. Org-scoped keys can attach non-access-controlled files to non-access-controlled projects. ## OpenAPI ````yaml POST /projects/{id}/files 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: /projects/{id}/files: post: tags: - Projects summary: Attach a file to a project description: >- Attach an already-uploaded file to a project. The file remains in its current folder; this only records the project link. Requires write access to the project and read access to the file. Org-scoped keys can attach non-access-controlled files to non-access-controlled projects. operationId: attachFileToProject parameters: - schema: type: string format: uuid description: The project ID required: true description: The project ID name: id in: path requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/AttachFileRequest' responses: '204': description: File attached (idempotent, repeat calls are no-ops) '400': description: Invalid request body 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: Invalid API key content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: Project not found, file not found, or insufficient write access 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: AttachFileRequest: type: object properties: file_id: type: string format: uuid description: ID of an already-uploaded file to attach to the project required: - file_id 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. ````