As a SWE at Rewe (at a completely different department), I can say that I find this pretty cool. I wonder if this is going to be a wakeup to management to relax the API restrictions.
This is the future of doing groceries. Let us login with our credentials and let us do the search/filling the cart with agents.
Totally fine to do the payment only on the web, so everyone can be sure they only order what was wished, and not 300 avocados.
I think a big issue here is the lack of standard - there is no established way of where an MCP server should be hosted so that agents are easily able to find it. Right now, the best solution I could think of would be to serve it at something like rewe.de/shop/mcp and you'd manually have to register it with your agent.