Create a Cart

Ensure you have a region ID, for example the default region ID

mutation createCart($defaultRegionId: ID!) {
    cart {
        createCart(input: {
            regionId: $defaultRegionId,
            currencyCode: "GBP"
        }) {
            errors { label message value }
            cart {
                id
            }
        }
    }
}

Will result in:

{
    "data": {
        "cart": {
            "createCart": {
                "errors": [],
                "cart": {
                    "id": "T3Bwb3J0dW5pdHk6OTQ4" # < -- COPY THIS!
                }
            }
        }
    }
}

Ensure you copy the returned cart id for subsequent mutations