UCP Checker & Agent Debugger

Find a store's UCP profile as you browse and see what it lets an AI agent do. Optionally shares profiles it finds with UCP Checker.

UCP Checker shows you what an agent finds on the store you're looking at. As you browse, the extension asks each store for its UCP profile at /.well-known/ucp. The badge on the toolbar tells you the answer before you click: OK: the store publishes a UCP profile and it reads cleanly. WARN: there is a profile, but something is wrong with it. NF: no UCP profile at /.well-known/ucp. ERR: something answered, but not a profile: a block or an error page. Click the badge to see: • The release the profile declares, and whether it is the latest UCP release or behind it. • Its capabilities, by short name (Checkout, Cart, Catalog Search). Anything outside the core UCP namespace shows who defines it. • Its payment handlers, with the same namespace labels. • Each endpoint (MCP, REST) on its own row, with a copy button. • For a profile that needs work: the first three problems in plain words, such as a profile that is not valid JSON, an endpoint without https, or a profile that is only reached through a redirect. The full list is on the store's status page. • What changed since your last visit: capabilities added or dropped, and release moves. From the popup you can open the store's status page on UCP Checker, run a fresh check, open the store in UCP Playground, view or copy the raw UCP profile, and, when the store declares catalog search, open it in the Catalog Validator. When a store has no profile, the popup links to the /.well-known/ucp guide and the UCP Validator, so you can see how to publish one. Who it's for • Agencies: check a client's store during an audit without opening developer tools. • Agent builders: confirm a store's MCP endpoint and release before you point an agent at it. • Partnerships: spot which brands are ready for agents as you browse, and share their public status page. What it can see Every request the extension makes goes without your cookies. • Host access: only https://*/.well-known/ucp • activeTab: the current tab's domain, nothing else on the page • webNavigation: to notice you've moved to a new page • storage: its results and your settings, on your device It never reads the page you're on or anything you type, your cookies or sign-in sessions, your browsing history, or private and incognito windows. Sharing, on by default When the extension finds a UCP profile, it sends UCP Checker the store's domain, the profile's address and the profile itself, with the time. Nothing about you or the page goes with it. Turn it off with the "Share what it finds" switch at the bottom of the popup. Free, no account. Works in Chrome, Edge and Brave. Support: https://ucpchecker.com/contact