# Get Custom Entities Metadata

The metadata is a JSON Schema document that lists the Custom Entities defined in the PIM
for the current tenant, together with their relationships. Use the returned denominators
to query individual Custom Entity schemas via `GET /CustomEntities('{denominator}')/$metadata`.
## Authentication
Requires a valid API key in the `X-API-KEY` header.
## Response
**200 OK** — Returns the JSON Schema as a `ServiceDocumentRepresentation`.
## Error Responses
- **401 Unauthorized** — Missing or invalid API key. Returned by the API gateway as
`{ "message": "Unauthorized", "request_id": "d8aafa5b8f3e400b60bea0123dd33317" }`.
- **404 Not Found** — Tenant not found.
- **500 Internal Server Error** — Unexpected technical error.

## Example
**Request:**

```http
GET /CustomEntities/$metadata HTTP/1.1
X-API-KEY: your-api-key-here
```
**Response:**

```http
HTTP/1.1 200 OK
Content-Type: application/json
```

Endpoint: GET /CustomEntities/$metadata
Version: 2.0.0

## Header parameters:

  - `X-API-KEY` (string)
    Tenant's API key (required)

## Response 200 fields (application/json):

  - `readLink` (object)

  - `readLink.uri` (string)

  - `value` (any)

## Response 401 fields (application/json):

  - `message` (string)

  - `request_id` (string)

## Response 404 fields (application/json):

  - `type` (string)

  - `title` (string)

  - `status` (integer)

  - `detail` (string)

  - `instance` (string)

## Response 500 fields (application/json):

  - `error` (string)

  - `details` (any)