Build the cart programmatically using the merchant's cart API or MCP cart tools, collecting item IDs, quantities, and any applied promo codes into a cart session.
Retrieve the cart's shareable checkout URL from the merchant API (many platforms return a persistent cart URL or token that can be resumed in a browser session).
Emit a human-in-the-loop (HITL) event to your agent orchestrator containing the checkout URL, itemized cart summary, total cost estimate, and the reason human authorization is required (e.g., payment method entry, address confirmation).
Pause the agent workflow and await a human-completed signal; set a timeout (e.g., 30 minutes) after which the agent re-notifies or cancels the pending cart.
Once the human-completed signal is received, verify order confirmation details (order ID, items, total) against the original cart to detect any changes made during human checkout.
Log the handoff event, human decision, and final order state for audit purposes.
Known gotchas
Cart sessions on many platforms expire after 15–60 minutes of inactivity; generate the checkout URL close in time to when you send the HITL notification, not at cart-build time.
The shareable cart URL may not transfer the cart across browsers or require the user to be logged in; test the handoff flow for your target merchant before deploying.
Never store or transmit payment card data within the agent system; the HITL handoff exists precisely so payment entry happens entirely within the merchant's PCI-compliant checkout UI.
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp