{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://ap2-protocol.org/schemas/types/checkout.json",
  "title": "Checkout",
  "description": "UCP Checkout object (dev.ucp.shopping.checkout 2026-04-08). The merchant field is an AP2 extension for mandate binding.",
  "type": "object",
  "additionalProperties": true,
  "required": [
    "id",
    "line_items",
    "status",
    "currency",
    "totals",
    "links"
  ],
  "properties": {
    "id": {
      "type": "string",
      "description": "Unique identifier of the checkout session."
    },
    "merchant": {
      "description": "The merchant associated with the checkout.",
      "$ref": "merchant.json"
    },
    "line_items": {
      "type": "array",
      "description": "Array of line items in the checkout.",
      "items": {
        "$ref": "line_item.json"
      }
    },
    "status": {
      "type": "string",
      "enum": [
        "incomplete",
        "requires_escalation",
        "ready_for_complete",
        "complete_in_progress",
        "completed",
        "canceled"
      ],
      "description": "Checkout state indicating the current phase."
    },
    "currency": {
      "type": "string",
      "description": "ISO-4217 3-letter alphabetic currency code."
    },
    "totals": {
      "type": "array",
      "description": "Pricing breakdown. Must contain exactly one subtotal and one total entry.",
      "items": {
        "$ref": "total.json"
      }
    },
    "links": {
      "type": "array",
      "items": {
        "$ref": "link.json"
      }
    },
    "buyer": {
      "$ref": "buyer.json",
      "description": "Representation of the buyer."
    },
    "messages": {
      "type": "array",
      "items": {
        "$ref": "message.json"
      },
      "description": "List of messages with error and info about the checkout session state."
    },
    "expires_at": {
      "type": "string",
      "format": "date-time"
    },
    "continue_url": {
      "type": "string",
      "format": "uri"
    }
  }
}