generated: '2026-09-04'
method: derived
source: mcp/willow-tools-list.json
note: >-
  Derived from the input schemas of the 13 tools the live UCP MCP endpoint returned on 2026-09-04.
  No OpenAPI exists for this provider, so response shapes are not enumerated — only entities and
  relationships the request schemas actually declare are recorded here. Fields no schema names are
  omitted rather than assumed.
identifier_scheme:
  format: Shopify global ID URNs
  examples:
    - gid://shopify/Checkout/abc123
  note: The checkout id format is stated in the tool descriptions; product and cart id formats are not.
entities:
  - name: Product
    description: A sale-ready item in Willow's storefront catalog.
    read_by:
      - search_catalog
      - lookup_catalog
      - get_product
    fields:
      - name: id
        type: string
        note: Product ID accepted by get_product and lookup_catalog.
      - name: selected
        type: array
        note: Selected variant options ({name, label}) used to resolve a variant.
      - name: categories
        type: array
        note: Filterable category membership.
      - name: price
        type: object
        note: Integer minor units + ISO 4217 currency; filterable by min/max.
      - name: available
        type: boolean
  - name: ProductVariant
    description: The purchasable form of a product; what a cart line item points at.
    fields:
      - name: id
        type: string
        note: "Referenced as line_items[].item.id — 'The Product Variant ID to add or update.'"
  - name: Cart
    description: A pre-checkout basket of line items for a buyer.
    written_by:
      - create_cart
      - update_cart
      - cancel_cart
    read_by:
      - get_cart
    fields:
      - name: id
        type: string
      - name: line_items
        type: array
      - name: buyer
        type: object
      - name: context
        type: object
  - name: LineItem
    description: One product variant and quantity inside a cart or checkout.
    fields:
      - name: id
        type: string
      - name: quantity
        type: integer
      - name: item.id
        type: string
        note: Product variant reference.
  - name: Buyer
    description: The person the agent is acting for.
    fields:
      - name: email
        type: string
      - name: phone_number
        type: string
  - name: Checkout
    description: A priced, addressable purchase in progress; completing it produces an Order.
    written_by:
      - create_checkout
      - update_checkout
      - complete_checkout
      - cancel_checkout
    read_by:
      - get_checkout
    fields:
      - name: id
        type: string
        note: 'gid://shopify/Checkout/...'
      - name: line_items
        type: array
      - name: buyer
        type: object
      - name: payment.instruments
        type: array
      - name: fulfillment.methods
        type: array
      - name: discounts.codes
        type: array
      - name: attribution
        type: object
        note: referring_domain, click_id_tag/value, activity_id_tag/value, utm_* parameters.
      - name: context
        type: object
  - name: PaymentInstrument
    description: A card, token or wallet credential bound to a checkout.
    fields:
      - name: id
        type: string
      - name: handler_id
        type: string
        note: One of the handlers in /.well-known/ucp.json — gpay, shopify.card, shop_pay, apple-pay.
      - name: type
        type: string
      - name: credential
        type: object
      - name: billing_address
        type: object
  - name: FulfillmentMethod
    description: A shipping (or other) delivery method attached to a checkout.
  - name: Discount
    description: A promo code applied to a cart or checkout; codes are case-insensitive and replace prior submissions.
  - name: Order
    description: The result of a completed checkout.
    read_by:
      - get_order
    note: Order reads require a signed agent JWT; no order write or refund operation is exposed.
relationships:
  - from: Cart
    to: LineItem
    type: has_many
    via: cart.line_items
  - from: Checkout
    to: LineItem
    type: has_many
    via: checkout.line_items
  - from: LineItem
    to: ProductVariant
    type: belongs_to
    via: line_items[].item.id
  - from: ProductVariant
    to: Product
    type: belongs_to
    via: catalog.selected variant options
  - from: Cart
    to: Buyer
    type: has_one
    via: cart.buyer
  - from: Checkout
    to: Buyer
    type: has_one
    via: checkout.buyer
  - from: Checkout
    to: PaymentInstrument
    type: has_many
    via: checkout.payment.instruments
  - from: Checkout
    to: FulfillmentMethod
    type: has_many
    via: checkout.fulfillment.methods
  - from: Checkout
    to: Discount
    type: has_many
    via: checkout.discounts.codes
  - from: Checkout
    to: Order
    type: has_one
    via: complete_checkout returns the order ID