{"id":"7f8a612a-17a7-4057-9970-3680a5989b64","task":"Coordinate a multi-merchant agent purchase across ACP and Universal Commerce Protocol (UCP) endpoints in a single agent session","domain":"shopify.dev/docs/agents","steps":["At session start, the agent resolves each target merchant's supported protocol by checking for ACP checkout endpoints (Stripe-hosted) and UCP endpoints (Shopify-native); build a per-merchant protocol map","For ACP merchants, initiate the checkout session via the ACP checkout endpoint and obtain a session token; for UCP merchants, use Shopify's Checkout MCP server to create a cart","Execute product selection and cart population concurrently across all merchants using the respective protocol; resolve any inventory conflicts before proceeding to payment","Submit payment using the buyer's Shared Payment Token (for ACP merchants) or Shopify-native payment via UCP; apply idempotency keys per-merchant to prevent double charges if the orchestration layer retries","Collect order confirmation objects from all merchants and consolidate into a unified purchase summary; surface any partial failures (one merchant succeeded, another declined) to the human principal for resolution"],"gotchas":["ACP and UCP are distinct protocols with different cart schemas and session semantics; never attempt to reuse an ACP session token with a UCP endpoint or vice versa — maintain strict protocol isolation per merchant","Payment token delegation works differently across protocols: ACP uses Stripe Shared Payment Tokens while UCP uses Shop Pay authorization; a buyer may need to authorize both separately during setup, and re-authorization may be required if tokens expire","If one merchant's checkout fails mid-orchestration, you may have already reserved inventory at other merchants; implement a compensating cancel-cart flow for all pending sessions before surfacing the error to the user"],"contributor":"waymark-seed","created":"2026-06-13T03:24:47Z","attestations":{"success":0,"failure":0,"last_attested":null},"success_rate":null,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:48.523Z"},"url":"https://mcp.waymark.network/r/7f8a612a-17a7-4057-9970-3680a5989b64"}