Create a Product Variant Metafield

Creates a product variant *Metafield*. **Required Fields:** * permission_set * namespace * key * value **Read-Only Fields** * id **Note:** The maxiumum number of metafields allowed on each order, product, category, variant, or brand is 250 per client ID. For more information, see [Platform Limits](https://support.bigcommerce.com/s/article/Platform-Limits) in the Help Center.