# StepUpBeginRequest

> Start a passkey assertion that proves presence for a sensitive action.

Start a passkey assertion that proves presence for a sensitive action.

## Fields

| Field | Type | Description |
| --- | --- | --- |
| `purpose` * | `approval`, `kill_switch`, `reveal_credentials`, `delete_resource`, `raise_spend_cap` |  |
| `subject_id` | string | The approval, database or other resource the assertion is bound to. |

\* always present

## Example

```json
{
  "purpose": "approval",
  "subject_id": "apr_01jbx2m9k7q4r8t5v6w3y0z1ap"
}
```

## Used by

- [Start a passkey assertion for a sensitive action](/docs/api/auth/#start-a-passkey-assertion-for-a-sensitive-action)