# Create a metafield definition validation

> Add a validation rule to a metafield definition.
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`POST /api/metafield_definition_validations`

Creates a MetafieldDefinitionValidation resource.

Adds a validation rule to a metafield definition. Reference the `metafieldDefinition`, the validation `name` (type) and its `value`. The rule must be compatible with the definition’s type, otherwise it is rejected with `422`.

## Request body

| Property              | Type     | Required | Description                                                            |
| --------------------- | -------- | -------- | ---------------------------------------------------------------------- |
| `metafieldDefinition` | `string` | Yes      | The metafield definition this validation belongs to.                   |
| `name`                | `string` | Yes      | The type of validation rule.                                           |
| `value`               | `string` | Yes      | The validation parameter value. Format depends on the validation type. |

## Response

**201** - MetafieldDefinitionValidation resource created

| Property              | Type     | Required | Description                                                            |
| --------------------- | -------- | -------- | ---------------------------------------------------------------------- |
| `@context`            | `object` | -        |                                                                        |
| `@id`                 | `string` | Yes      |                                                                        |
| `@type`               | `string` | Yes      |                                                                        |
| `id`                  | `string` | -        | The resource's unique identifier (UUID).                               |
| `metafieldDefinition` | `string` | Yes      | The metafield definition this validation belongs to                    |
| `name`                | `string` | Yes      | The type of validation rule                                            |
| `value`               | `string` | Yes      | The validation parameter value. Format depends on the validation type. |

## Errors

**400** - Invalid input

| Property      | Type              | Required | Description                                                                                                                          |
| ------------- | ----------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------ |
| `@context`    | `object`          | -        |                                                                                                                                      |
| `@id`         | `string`          | Yes      |                                                                                                                                      |
| `@type`       | `string`          | Yes      |                                                                                                                                      |
| `title`       | `string \| null`  | -        | A short, human-readable summary of the problem.                                                                                      |
| `detail`      | `string \| null`  | -        | A human-readable explanation specific to this occurrence of the problem.                                                             |
| `status`      | `integer \| null` | -        |                                                                                                                                      |
| `instance`    | `string \| null`  | -        | A URI reference that identifies the specific occurrence of the problem. It may or may not yield further information if dereferenced. |
| `type`        | `string`          | -        | A URI reference that identifies the problem type                                                                                     |
| `description` | `string \| null`  | -        |                                                                                                                                      |

**403** - Access denied. The caller is missing one or more identity permissions required for this operation.

| Property             | Type       | Required | Description                                                                                                                                |
| -------------------- | ---------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| `@context`           | `object`   | -        |                                                                                                                                            |
| `@id`                | `string`   | Yes      |                                                                                                                                            |
| `@type`              | `string`   | Yes      |                                                                                                                                            |
| `type`               | `string`   | -        |                                                                                                                                            |
| `title`              | `string`   | -        |                                                                                                                                            |
| `status`             | `integer`  | -        |                                                                                                                                            |
| `detail`             | `string`   | -        |                                                                                                                                            |
| `missingPermissions` | `string[]` | -        | Identity permissions that the caller is missing for this operation. Present only when the 403 is caused by a denied identity:* permission. |

**422** - An error occurred

| Property      | Type             | Required | Description |
| ------------- | ---------------- | -------- | ----------- |
| `@context`    | `object`         | -        |             |
| `@id`         | `string`         | Yes      |             |
| `@type`       | `string`         | Yes      |             |
| `status`      | `integer`        | -        |             |
| `violations`  | `object[]`       | -        |             |
| `detail`      | `string`         | -        |             |
| `description` | `string`         | -        |             |
| `type`        | `string`         | -        |             |
| `title`       | `string \| null` | -        |             |
| `instance`    | `string \| null` | -        |             |

## Examples

### Example request

```bash
curl -X POST 'https://<tenant>.product-management.flowkiwi.net/api/metafield_definition_validations' \
  -H 'Authorization: Bearer {access_token}' \
  -H 'Flowkiwi-Api-Version: 2026-07' \
  -H 'Accept: application/ld+json' \
  -H 'Content-Type: application/ld+json' \
  -d '{
  "metafieldDefinition": "/api/metafield_definitions/019afb01-1a2b-7c3d-8e4f-0a1b2c3d4e5f",
  "name": "/api/metafield_definition_validation_types/max_length",
  "value": "500"
}'
```

### Example response

```json
{
  "@context": "/api/contexts/MetafieldDefinitionValidation",
  "@id": "/api/metafield_definition_validations/019afe01-1a2b-7c3d-8e4f-0a1b2c3d4e5f",
  "@type": "MetafieldDefinitionValidation",
  "id": "019afe01-1a2b-7c3d-8e4f-0a1b2c3d4e5f",
  "metafieldDefinition": "/api/metafield_definitions/019afb01-1a2b-7c3d-8e4f-0a1b2c3d4e5f",
  "name": "/api/metafield_definition_validation_types/max_length",
  "value": "500"
}
```