{"jsonrpc": "2.0", "id": 4, "method": "tools/call", "params": {"name": "create_cart", "arguments": {"meta": {"ucp-agent": {"profile": "https://shopify.dev/ucp/agent-profiles/examples/2026-08-25/valid-with-capabilities.json"}}, "cart": {"line_items": [{"item": {"id": "gid://shopify/ProductVariant/41577478553733"}, "quantity": 1}], "context": {"address_country": "US", "postal_code": "10001", "currency": "USD"}}}}}