> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hydradb.com/llms.txt
> Use this file to discover all available pages before exploring further.

# List Collections

> List collection IDs inside a database.

1. The default collection is not created until the first write - no collection exists until then. Once you ingest without an explicit `collection`, the default collection is created and stores all context written without a `collection`. Create additional collections at any time to scope data to users, teams, or projects.
2. **Implicit creation.** Collections are auto-created when ingestion writes data under a new `collection`. The returned list grows organically as your application writes data under new values.

<RequestExample>
  ```python Python SDK theme={"dark"}
  response = client.databases.collections(database="your database id")
  ```

  ```typescript TypeScript SDK theme={"dark"}
  const response = await client.databases.collections({
    database: "my_first_database",
  });
  ```

  ```bash cURL theme={"dark"}
  curl -X GET 'https://api.hydradb.com/databases/collections?database=my_first_database' \
    -H "Authorization: Bearer <your_api_key>" \
    -H "API-Version: 2"
  ```
</RequestExample>

<ResponseExample>
  ```json Success theme={"dark"}
  {
    "success": true,
    "data": {
      "collections": ["user_alex", "user_johndoe", "workspace_42", "collection_default_abc123"],
      "message": "Successfully retrieved collection IDs"
    },
    "error": null,
    "meta": {
      "request_id": "9d13aef4-02f4-4e73-8c62-4c2601d04f9d",
      "latency_ms": 12.3
    }
  }
  ```

  ```json Empty database theme={"dark"}
  {
    "success": true,
    "data": {
      "collections": [],
      "message": "Successfully retrieved collection IDs"
    },
    "error": null,
    "meta": {
      "request_id": "9d13aef4-02f4-4e73-8c62-4c2601d04f9d",
      "latency_ms": 12.3
    }
  }
  ```

  ```json Failure theme={"dark"}
  {
    "success": false,
    "data": null,
    "error": {
      "code": "DATABASE_NOT_FOUND",
      "message": "Database not found"
    },
    "meta": {
      "request_id": "9d13aef4-02f4-4e73-8c62-4c2601d04f9d",
      "latency_ms": 4.8
    }
  }
  ```
</ResponseExample>

<div className="api-before-related-resources" />

<Tip>
  **Related Resources**

  * **Inspect content:** [List Documents](/api-reference/v2/endpoint/list-documents) - scoped to a `collection`
  * **Inspect usage:** [Database Stats](/api-reference/v2/endpoint/tenant-stats)
</Tip>


## OpenAPI

````yaml api-reference/v2/openapi.json GET /databases/collections
openapi: 3.1.0
info:
  contact:
    email: support@hydradb.com
    name: HydraDB Support
  description: >-
    HydraDB Application API — knowledge ingestion, search, and memory
    management.
  license:
    name: Proprietary
  title: HydraDB Application API
  version: 0.1.0
servers:
  - description: Production server
    url: https://api.hydradb.com
security: []
externalDocs:
  description: ''
  url: ''
paths:
  /databases/collections:
    get:
      tags:
        - database-management
      summary: List collections
      description: List all collections for a given database
      parameters:
        - description: Database identifier
          in: query
          name: database
          required: true
          schema:
            example: acme_corp
            type: string
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/handler.Envelope-tenants_SubTenantIdsResponse
          description: OK
        '400':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/handler.ErrorResponse'
          description: Bad Request
        '404':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/handler.ErrorResponse'
          description: Not Found
        '500':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/handler.ErrorResponse'
          description: Internal Server Error
      security:
        - BearerAuth: []
components:
  schemas:
    handler.Envelope-tenants_SubTenantIdsResponse:
      properties:
        data:
          $ref: '#/components/schemas/tenants.SubTenantIdsResponse'
          example:
            collections:
              - team_docs
              - engineering
            message: Success
            sub_tenant_ids:
              - sub_tenant_4567
              - sub_tenant_8901
        error:
          $ref: '#/components/schemas/handler.apiError'
          description: Error message, empty string on success.
          example:
            code: DATABASE_NOT_FOUND
            message: Database not found
        meta:
          $ref: '#/components/schemas/handler.responseMeta'
          example:
            collection: team_docs
            database: acme_corp
            latency_ms: 12.3
            request_id: 9d13aef4-02f4-4e73-8c62-4c2601d04f9d
            source_type: file
            sub_tenant_id: sub_tenant_4567
            tenant_id: tenant_1234
        success:
          description: Whether the request succeeded.
          example: true
          type: boolean
      type: object
    handler.ErrorResponse:
      properties:
        detail:
          $ref: '#/components/schemas/handler.ErrorDetail'
          description: Structured error detail with code, message, and deprecation hints.
          example:
            deprecated: true
            deprecated_field: tenant_id
            error_code: VALIDATION_ERROR
            message: Request validation failed
            preferred_field: database
            success: true
      type: object
    tenants.SubTenantIdsResponse:
      properties:
        collections:
          description: List of collection identifiers for this database.
          example:
            - team_docs
            - engineering
          items:
            type: string
          type: array
          uniqueItems: false
        message:
          description: Human-readable result message.
          example: Success
          type: string
        sub_tenant_ids:
          deprecated: true
          description: Deprecated alias for `collections`.
          example:
            - sub_tenant_4567
            - sub_tenant_8901
          items:
            type: string
          type: array
          uniqueItems: false
          x-deprecated: 'true'
      type: object
    handler.apiError:
      properties:
        code:
          description: Machine-readable error code (e.g. `DATABASE_NOT_FOUND`).
          example: DATABASE_NOT_FOUND
          type: string
        message:
          description: Human-readable description of the error.
          example: Database not found
          type: string
      type: object
    handler.responseMeta:
      properties:
        collection:
          description: >-
            Collection scope. Defaults to the default collection when omitted.
            Formerly `sub_tenant_id`; the `sub_tenant_id` alias is still
            accepted (deprecated).
          example: team_docs
          type: string
        database:
          description: >-
            Owning database. Formerly `tenant_id`; the `tenant_id` alias is
            still accepted (deprecated).
          example: acme_corp
          type: string
        deprecation:
          description: >-
            Deprecation lists any migration nudges that apply to this request —
            the

            caller used a legacy /tenants route, a legacy
            tenant_id/sub_tenant_id field,

            or the deprecated sub_tenant_ids selector. It is a non-breaking
            signal (the

            status code is unchanged); omitempty keeps it absent for
            fully-migrated

            requests. A list so independent deprecations coexist without
            clobbering.
          items:
            $ref: '#/components/schemas/handler.deprecationNotice'
          type: array
          uniqueItems: false
        latency_ms:
          description: Server-side processing time in milliseconds.
          example: 12.3
          type: number
        request_id:
          description: Unique identifier for this request, useful for support and tracing.
          example: 9d13aef4-02f4-4e73-8c62-4c2601d04f9d
          type: string
        source_type:
          description: Type of the parent source (e.g. `file`, `slack`, `notion`).
          example: file
          type: string
        sub_tenant_id:
          deprecated: true
          example: sub_tenant_4567
          type: string
          x-deprecated: 'true'
        tenant_id:
          deprecated: true
          example: tenant_1234
          type: string
          x-deprecated: 'true'
      type: object
    handler.ErrorDetail:
      properties:
        deprecated:
          description: Whether this response concerns a deprecated field or route.
          example: true
          type: boolean
        deprecated_field:
          description: The deprecated field name.
          example: tenant_id
          type: string
        error_code:
          description: Machine-readable error classification code.
          example: VALIDATION_ERROR
          type: string
        message:
          description: Human-readable description of the error.
          example: Request validation failed
          type: string
        preferred_field:
          description: The canonical replacement for the deprecated field.
          example: database
          type: string
        success:
          description: Always false for error responses.
          example: true
          type: boolean
      type: object
    handler.deprecationNotice:
      properties:
        deprecated:
          description: Whether this response concerns a deprecated field or route.
          example: true
          type: boolean
        deprecated_field:
          description: The deprecated field name.
          example: tenant_id
          type: string
        deprecated_since:
          description: API version when the field was deprecated.
          example: 2.0.1
          type: string
        message:
          description: Migration guidance message.
          example: tenant_id is deprecated; use database instead.
          type: string
        preferred_field:
          description: The canonical replacement for the deprecated field.
          example: database
          type: string
      type: object
  securitySchemes:
    BearerAuth:
      bearerFormat: API key
      description: 'API key sent as a Bearer token: "Bearer prefix.secret"'
      scheme: bearer
      type: http

````