# Assert

Raises an error if the input is not true, otherwise returns the input. Assert lives in the **Custom** category of the `fx` menu.

## Parameter

| Parameter | Type   | Required | Default | Description                                            |
| --------- | ------ | -------- | ------- | ------------------------------------------------------ |
| Input     | string | yes      | —       | Value to transform. Previous step output or a literal. |

`Input` is the primary value (previous step output or a literal).

## Returned value

| Type     | Description                          |
| -------- | ------------------------------------ |
| `string` | Result of the Assert transformation. |

## Example

<details>
<summary>Run Assert</summary>

Raises an error if the input is not true, otherwise returns the input Adjust optional parameters when the defaults do not match your payload.

1. Set **Input** to the value to transform (previous step output or a literal).

2. Confirm **Output value** shows the transformed result.

</details>