UCP is genuinely interesting, but I think it mostly trades one form of lock-in for another. Google and Shopify are pushing protocols like UCP and ACP because they can see AI eating the marketplace middleman. As discovery and checkout move into conversational interfaces, Google Shopping and Shopify’s own “Shop” app are at risk, and UCP is a way for them to stay central in that shift.

The issue is that UCP mainly benefits platforms that are already part of that ecosystem. Instead of Amazon et al controlling discovery, you risk ending up with Google and Shopify doing it through AI-driven interfaces. The experience looks more open, but control still sits with a small number of large platforms.

I’m working on something similar with a different premise. We’re building an open-source marketplace stack, basically a Shopify per vertical, where sellers run their own storefronts and discovery happens directly against the shop’s own API. You can see a working interoperable marketplace here[0], built on our first Shopify alternative, Openfront. Our website[1] goes deeper into the different vertical marketplaces we’re building like hotels, grocery stores, etc. We started with MCP-UI[2] for native conversational commerce, and V2 will support UCP, but it’s optional rather than the foundation.

[0] https://marketplace.openship.org

[1] https://openship.org

[2] https://mcpui.dev