# Assertions

Checks across the fields of one extract.

| Key | Type | Description |
|---|---|---|
| `$asserts` | `object[]` | Cross-field checks at the schema root. A failing assert warns `out_of_range` on its `left` field under that field's policy, or fails the job when `policies.strict` is on. |
| `$asserts.left` | `string` | The field path on the left side, such as `price` or `products[].price`. |
| `$asserts.op` | `"<" \| "<=" \| "==" \| "!=" \| ">=" \| ">"` | The comparison: `<`, `<=`, `==`, `!=`, `>=` or `>`. |
| `$asserts.right` | `string or number or boolean or null` | A field path, or a literal string, number, boolean or `null`. |