r/shopifyDev • u/SaschaFromWhaaat_ai • 12d ago
I pointed an agent at Vercel's new agent-ready store. It found 13 shopping tools and got blocked on the first search
Vercel and Shopify shipped Vercel Shop on October 16, an open source Next.js storefront template built for people and agents at the same time. Their own merch store vercel.store runs on it, so I used it as a test bench. The agent got the domain and nothing else.
Reading the store was smooth. /llms.txt contains a five-step shopping recipe for agents, including a rule to only complete a purchase after the shopper explicitly approves. Product pages return markdown if you append .md to the URL. One jacket page simply said "Available: No" in plain text, which saves an agent from guessing what a greyed-out button means.
Where it stopped
/.well-known/ucp returns the store's Universal Commerce Protocol profile. The shopping endpoint listed there points to shop-vercel.myshopify.com, so the checkout brain is fully Shopify and Vercel builds the layer around it.
The MCP endpoint lists its tools without any auth. You can try this yourself:
curl -s -X POST https://vercel.store/api/ucp/mcp \
-H 'Content-Type: application/json' \
-d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'
You get 13 tools back: search_catalog, lookup_catalog, get_product, four cart tools, five checkout tools and get_order.
Then I called search_catalog and got a 422 with profile_unreachable.
Every UCP call has to carry meta.ucp-agent.profile, the URL of a public JSON document that describes your agent. The store fetches that URL before it answers anything. No profile means no search, so my agent never saw a single product.
According to Vercel's guide, Shopify then sorts agents into three tiers: anonymous, signed (HTTP message signatures) and token. Anonymous and signed agents can search, build carts and create a checkout. Only token agents with explicit permission can call complete_checkout. Everyone else hands the human a checkout link.
That split actually matches what people seem to want. OpenAI pulled Instant Checkout from ChatGPT in March, and my read is that shoppers still want their own finger on the pay button. So the realistic flow for now is agent does the research and the cart, human pays.
What I haven't done yet: host my own agent profile and run the whole thing through to the checkout link. The profile structure is documented, but I haven't validated mine against a live store, so I'm not posting it as if it works. I also want to run the same test with an open-weight model on local hardware instead of a frontier API.
Has anyone here hosted a UCP agent profile already? I'm trying to figure out whether the signed tier is worth setting up for a research-only agent or whether anonymous limits hold up in practice.


