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

# GET /datasets/{id}/columns — List Dataset Columns

> Retrieve just the column schema of a dataset — name, ID, data type, and whether the column is an entity/dimension — without the rest of the dataset metadata.

Returns the column definitions for a dataset as a standalone array. Use this endpoint when you only need to inspect the schema — for example, to build a `$select` list for the [download endpoint](/api/datasets/data) or to validate that a column name exists before referencing it in an OData filter. The full dataset metadata (description, source, date range) is available from [`GET /datasets/{id}`](/api/datasets/get) instead.

## Authentication

Authenticate using HTTP Basic Auth. Pass your API key as the username and leave the password empty. You must have at least `Read` permission on the dataset.

## Request

**Method:** `GET`
**URL:** `https://api.alphacast.io/datasets/{dataset_id}/columns`

## Path parameters

<ParamField path="dataset_id" type="integer" required>
  The numeric ID of the dataset whose columns you want to retrieve.
</ParamField>

## Response

Returns an array of column definition objects. Each object has the same shape as the entries in the `columns` array returned by [`GET /datasets/{id}`](/api/datasets/get).

<ResponseField name="id" type="integer">
  Unique column ID. Use this value with `$select` to reference columns reliably across renames.
</ResponseField>

<ResponseField name="name" type="string">
  Column display name.
</ResponseField>

<ResponseField name="dataType" type="string">
  Data type of the column. One of `Date`, `String`, or `Decimal`.
</ResponseField>

<ResponseField name="isEntity" type="boolean">
  When `true`, this column is a dimension or index column (e.g., `Date`, `Country`). When `false`, it is a value column.
</ResponseField>

## Examples

<RequestExample>
  ```bash cURL theme={null}
  curl -u YOUR_API_KEY: https://api.alphacast.io/datasets/123/columns
  ```

  ```python Python theme={null}
  import requests

  response = requests.get(
      "https://api.alphacast.io/datasets/123/columns",
      auth=("YOUR_API_KEY", ""),
  )
  columns = response.json()
  ```

  ```javascript Node.js theme={null}
  const response = await fetch("https://api.alphacast.io/datasets/123/columns", {
    headers: { Authorization: "Basic " + btoa("YOUR_API_KEY:") },
  });
  const columns = await response.json();
  ```
</RequestExample>

<ResponseExample>
  ```json 200 theme={null}
  [
    { "id": 1, "name": "Date", "dataType": "Date", "isEntity": true },
    { "id": 2, "name": "Country", "dataType": "String", "isEntity": true },
    { "id": 3, "name": "GDP", "dataType": "Decimal", "isEntity": false },
    { "id": 4, "name": "Population", "dataType": "Decimal", "isEntity": false }
  ]
  ```

  ```json 404 theme={null}
  {
    "message": "Dataset not found"
  }
  ```
</ResponseExample>

## Error responses

| Status             | Cause                                                           |
| ------------------ | --------------------------------------------------------------- |
| `401 Unauthorized` | No API key provided and the dataset is not publicly accessible. |
| `403 Forbidden`    | Your account does not have read access to this dataset.         |
| `404 Not Found`    | No dataset exists with the given ID.                            |

<Tip>
  To use a column with `$select` on the download endpoint, prefer the numeric `id` over the `name` — IDs are stable across column renames, so download links remain valid even if the schema is reorganised.
</Tip>