Build an agent application that uses ACP's April 2026 Cart, Feed, Orders, and MCP capabilities to manage the full purchase lifecycle via the updated protocol
Review the ACP changelog for the April 17, 2026 release which added Cart, Feed, Orders, Authentication, and MCP capabilities to the protocol; pull the latest spec from github.com/agentic-commerce-protocol/agentic-commerce-protocol.
Implement the Cart endpoint (POST /cart) which replaced the earlier single-step checkout session in the updated spec; the cart allows multi-item accumulation, shipping option selection, and discount application before triggering payment.
Subscribe to the Orders feed endpoint so your agent can poll or receive webhooks on order status changes (confirmed, shipped, delivered, cancelled) using the new Orders capability added in April 2026.
Implement the ACP Authentication flow for the MCP capability: ACP now supports MCP server connections as of the April update, allowing agents to call merchant tools directly via MCP rather than only REST; authenticate using the OAuth 2.0 client credentials flow specified in the Authentication capability.
Test the full lifecycle: feed product discovery → cart creation → cart update → checkout (via Stripe SPT) → order status polling; use the ACP sandbox environment for end-to-end testing before pointing to production merchant endpoints.
Known gotchas
The January 2026 (capability negotiation) and January 30, 2026 (extensions, discounts, payment handlers) updates are prerequisites for the April 2026 Cart/MCP update; a server that only implements the original spec will reject Cart and Orders requests.
ACP's MCP capability requires both the agent and merchant to support MCP as a transport; existing REST-only ACP integrations continue to work over the REST path and do not need to adopt MCP unless they need the tool-call interaction model.
OpenAI and Stripe are the Founding Maintainers of the ACP specification; changes to the spec are governed through the github.com/agentic-commerce-protocol organization, not through Stripe's or OpenAI's individual documentation channels.
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