Is WebMCP a standard?

It is a proposal developed in the open. Check the spec's current status before relying on it.

How does ARC detect it?

From the page's HTML. ARC does not complete a purchase.

What is WebMCP and do stores use it?

WebMCP lets a web page expose tools that an AI agent in the browser can call, like reading a cart or completing checkout, instead of clicking around the page. ARC detects WebMCP on store pages. Its Protocol Matrix shows how many checked stores declare it, mainly through Shopify's storefront adapter.

What WebMCP is

WebMCP is a proposal for a web page to register tools with the browser, so an agent in the tab can call them instead of clicking. Shopify ships a storefront adapter. The draft is the W3C Web Machine Learning Community Group note. Whether it is a finished standard is the spec's status, which you should read there.

How it differs from a protocol profile like UCP

A UCP profile is a file on the store's domain that any HTTP client can fetch. WebMCP is tools in the page, for an agent in the browser. A store can have one, both, or neither.

What ARC detects

ARC reads the server HTML for Shopify's adapter. It does not open a live browser session to call the tools, and it does not buy anything. Checkout WebMCP (get, update, complete) is a separate HTML check. Those tools say the buyer must approve completion.

Live numbers

ARC saved checks, accessed 2026-10-13

Declared: 1,680 of 4,307 (39%)MeasuredWebMCP adapter found in server HTML

Valid: Not measuredNot measuredNot checked (no live browser session)

Usable: Not measuredNot measuredNot checked (no live browser session)

Transacts: 39 of 51 (76.5%)InferredIndex stores with WebMCP where at least one browser shopper reached the cart

Transacts here is Inferred: Index stores where the adapter was found and at least one browser shopper reached the cart. That links two observations. It is not proof the shopper used WebMCP.

Buyer approval and safety

The checkout tools ARC detects require buyer approval. ARC does not complete a purchase through them.

Frequently asked questions

What is WebMCP and do stores use it?: WebMCP lets a web page expose tools that an AI agent in the browser can call, like reading a cart or completing checkout, instead of clicking around the page. ARC detects WebMCP on store pages. Its Protocol Matrix shows how many checked stores declare it, mainly through Shopify's storefront adapter.
Is WebMCP a standard?: It is a proposal developed in the open. Check the spec's current status before relying on it.
Does WebMCP buy things automatically?: The checkout tools ARC detects require buyer approval.
How does ARC detect it?: From the page's HTML. ARC does not complete a purchase.

On ARC

Cite this: ARC, arcreport.ai, accessed 2026-10-13, CC-BY-4.0. Protocol figures: ARC saved checks, accessed 2026-10-13 (13 October 2026). Index browser figures: ARC open dataset snapshot 2026-10-12. Platform figures: ARC saved checks, accessed 2026-10-13.

Every figure is labelled Measured, Inferred or Not measured. Not measured is not zero. A missing result is not a mark against a store. ARC stops before payment.