# Adding Items to Cart

Adding an item to a Cart is the first step of the Checkout process. You can do this either during Cart creation or through a dedicated API during the checkout process.

{% hint style="info" %}
Violet recommends adding SKUs during cart creation. This is because any call that changes a cart also makes an underlying call to relevant merchant stores and impacts your rate limits.
{% endhint %}

## Create Cart + Add Item to Cart

In addition to other inputs, the [Create Cart](https://app.gitbook.com/s/8lXIp71Ct5qCUhXjko2q/orders-and-checkout/carts/create-cart) endpoint also takes in a list of SKUs along with their quantity as seen below:

```json
"skus": [
    {
        "sku_id": 10000,
        "quantity": 1
    }
  ]
```

If provided, the `Cart` created will include these these items. In the example response below, an item was added from `The Violet Garden`, one of the stores we have available in sandbox to place orders against.

```json
{
    "id": 74909,
    "token": "f43a41f11ea34a06a1c247934f038d0f",
    "user_id": 10397,
    "app_id": 10382,
    "developer_id": 10292,
    "bags": [
        {
            "id": 60593,
            "order_id": 74909,
            "merchant_id": 10189,
            "app_id": 10382,
            "status": "IN_PROGRESS",
            "fulfillment_status": "PROCESSING",
            "financial_status": "UNPAID",
            "skus": [
                {
                    "id": 79315,
                    "merchant_id": 10189,
                    "app_id": 10382,
                    "product_id": "87f88388d8a44de6b7ea74d1b822926f",
                    "sku_id": 196585,
                    "external_id": "45101059440941",
                    "name": "Pastel Flower Land - Extra-Large / Design Three / Blue",
                    "brand": "The Violet Garden",
                    "thumbnail": "https://cdn.shopify.com/s/files/1/0758/9363/7421/files/wealthy_floral_design_tshirt_with_a_blue_pastel_colour_backgrou_caefa8e2-b19a-4eb7-84a1-1855591d017b.png",
                    "quantity": 1,
                    "price": 3500,
                    "weight": 3.0,
                    "available": true,
                    "status": "IN_PROGRESS",
                    "product_type": "PHYSICAL",
                    "line_price": 3500
                }
            ],
            "taxes": [],
            "sub_total": 3500,
            "taxes_included": false,
            "transactions": [],
            "external_checkout": true,
            "commission_rate": 25.0,
            "date_created": "2023-09-14T19:49:51+0000",
            "remorse_period_ends": "2023-10-14T19:49:51+0000",
            "currency": "USD",
            "external_currency": "USD",
            "channel": "APP",
            "platform": "SHOPIFY",
            "fulfillments": [],
            "discounts": [],
            "wallet_based_checkout": false,
            "bag_id": 60593,
            "bag_status": "IN_PROGRESS",
            "merchant_name": "the violet garden"
        }
    ],
    "sub_total": 3500,
    "status": "IN_PROGRESS",
    "is_guest": true,
    "date_created": "2023-09-14T19:49:51+0000",
    "date_last_modified": "2023-09-14T19:49:51+0000",
    "priced": false,
    "wallet_based_checkout": false,
    "currency": "USD",
    "errors": [],
    "channel": "APP",
    "currency_symbol": "$",
    "stripe_key": "pk_test_UHg8oLvg4rrDCbvtqfwTE8qd",
    "order_id": 74909,
    "intent_based_checkout": false,
    "guest": true,
    "order_status": "IN_PROGRESS"
}
```

***

## Add Item to Cart

The [Add SKU to Cart](https://app.gitbook.com/s/8lXIp71Ct5qCUhXjko2q/orders-and-checkout/cart-items/add-sku-to-cart) API lets you add items to a cart at any point up until a `Cart` has been submitted.

In this scenario, only one SKU can be added at a time. A sample body can be seen below:

```json
{
      "sku_id": 10000,
      "quantity": 1
}
```

The response for this call will be similar to the one above.

{% hint style="info" %}
When adding a `Sku` to a cart, a line item entity called an `OrderSku` is created. When making modifications to a line item in a cart, you will be interacting with the `OrderSku`, which has a different `id` to the original `Sku`. You can find the `id` of the original `Sku` in the `sku_id` property of the `OrderSku`.
{% endhint %}

***

## Custom Properties

Custom properties, also commonly referred to as "metadata", can be applied to any new line item or existing line in in a cart.

* Any endpoint that allows for the addition or modification of an `OrderSku` will accept a list of one or more custom properties.
* Custom properties can be removed from an `OrderSku` by setting the value of `custom_properties` to `null` or `[]`.

Custom properties have the following structure.

```json
{
  "name": "string", // required
  "value": "string" // required
}
```

The following example shows how custom properties can be applied to a new `OrderSku` while it's being added to a cart.

`POST /v1/checkout/cart/{cart_id}/skus`

```json
{
  "sku_id": 99999,
  "quantity": 1,
  "custom_properties": [
    {
      "name": "sample name",
	  "value": "sample value"
	}
  ]
}
```

{% hint style="warning" %}
Some commerce platforms do not support the concept of custom properties on a line item. For these platforms, the data will persist on the Violet OrderSku, but will not be forwarded to the commerce platform. Because these platforms do not support custom properties, there will be no merchants on these platforms with requirements for custom properties. These platforms currently include `BIGCOMMERCE`, `WIX`, and `DEMANDWARE` (also known as Salesforce Commerce Cloud).
{% endhint %}