# Function: checkRules()

```ts
function checkRules(rules, at?): string | null;
```

Defined in: [packages/core/src/records/rules.ts:49](https://github.com/leifriksheim/minca/blob/main/core/src/records/rules.ts#L49)

Why a set of rules is malformed, or null when it is not

## Parameters

| Parameter | Type | Default value |
| ------ | ------ | ------ |
| `rules` | `unknown` | `undefined` |
| `at?` | `string` | `'rules'` |

## Returns

`string` \| `null`