# Function: checkActionInput()

```ts
function checkActionInput(action, input): string | null;
```

Defined in: [packages/core/src/node/actions.ts:1013](https://github.com/leifriksheim/minca/blob/main/core/src/node/actions.ts#L1013)

Why an input does not fit an action's schema, or null when it does.

## Parameters

| Parameter | Type |
| ------ | ------ |
| `action` | [`NodeAction`](https://minca.dev/api/core/interfaces/NodeAction.md) |
| `input` | `unknown` |

## Returns

`string` \| `null`