With Types, you can model your own Custom Fields on the following resources and data types.

Enumeration Members

Address: "address"
ApprovalFlow: "approval-flow"
ApprovalRule: "approval-rule"
Asset: "asset"
AssociateRole: "associate-role"
BusinessUnit: "business-unit"
CartDiscount: "cart-discount"
Category: "category"
Channel: "channel"
Customer: "customer"
CustomerGroup: "customer-group"
CustomLineItem: "custom-line-item"
DiscountCode: "discount-code"
InventoryEntry: "inventory-entry"
LineItem: "line-item"
Order: "order"
OrderDelivery: "order-delivery"
OrderEdit: "order-edit"
OrderParcel: "order-parcel"
OrderReturnItem: "order-return-item"
Payment: "payment"
PaymentInterfaceInteraction: "payment-interface-interaction"
ProductPrice: "product-price"
ProductSelection: "product-selection"
ProductTailoring: "product-tailoring"
Quote: "quote"
Review: "review"
Shipping: "shipping"
ShippingMethod: "shipping-method"
ShoppingList: "shopping-list"
ShoppingListTextLineItem: "shopping-list-text-line-item"
StandalonePrice: "standalone-price"
Store: "store"
Transaction: "transaction"