> ## 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**.


    ## Current Limitations


    The API is optimized for single-turn completions. The following are not yet
    available via API:


    - **Multi-turn conversations**: each request is independent

    - **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: Projects
    description: Project management endpoints
  - name: Utility
    description: Health check and connectivity 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'
        '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
        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.

````