{
  "endpoint": "POST /agentic_commerce/update_checkout",
  "description": "ACP Update Checkout - Modify line items, shipping, or customer details",
  "spec_version": "2026-01-30",
  "request": {
    "checkout_id": "string - Checkout session ID",
    "line_items": "array - Updated line items (optional)",
    "shipping_method": "string - Selected shipping option (optional)",
    "customer": "object - Updated customer details (optional)"
  },
  "response": {
    "checkout_id": "chk_demo_abc123",
    "status": "pending",
    "line_items": [],
    "subtotal": 8500,
    "shipping": 500,
    "tax": 765,
    "total": 9765,
    "currency": "usd",
    "updated_at": "2026-02-15T10:35:00Z"
  },
  "demo": true
}