WebMCP Tools

Who this is for: an agent acting for the customer, running in the browser tab they are ordering in. When an AI agent in a customer’s browser helps them order, it otherwise has to read the page’s markup and simulate clicks — slow, and wrong as soon as the layout changes. WebMCP is a proposed web standard that takes the direct route: the page registers tools with the browser, and the agent calls them with structured arguments and gets structured data back. A storekit ordering page registers its tools with the browser through document.modelContext. There is nothing to install and no key to obtain: an agent that supports WebMCP finds the tools on the page it is already on.

​

How It Works

The tools act on the tab the customer is looking at, not on a copy of it.

• Reads answer from the page’s own state — the venue that is loaded, the menu as it is filtered for this customer, the basket as it stands. An agent is never told an item is orderable that the page would refuse.
• Writes go through the same actions the page’s own buttons use, so a line an agent adds behaves like one the customer added: the same pricing, the same option validation, the same basket the customer sees update in front of them.
• Prices come back as formatted strings in the venue’s currency, and descriptions are stripped of markup and truncated. Results are for reading aloud, not for rendering.

Nothing leaves the tab. There is no MCP server involved and no transport: the agent calls a JavaScript function in the page.

​

Tools

The agent picks a tool from its description. Every tool below is registered on every ordering page where WebMCP is enabled.

​

Venue and Menu

​

Basket

The three basket tools are the only writes, and they are marked as writes — a client that respects readOnlyHint asks the customer before calling one. Payment, discount codes and opening checkout are not exposed: the customer reviews and pays on the page. Items are named to a write by the id the reads publish, with any chosen options in brackets — BURGER(CHEESE;BACON:2) — the same grammar the basket prefill links use. An item whose options are nested more than one level deep is returned with a link to its page instead, because a choice tree that deep produces baskets nobody ordered.

​

Where the Tools Are Available

The page also opts into an origin-isolated agent cluster, which WebMCP requires. Nothing is downloaded on a browser without WebMCP: feature detection happens first, and the tools are fetched only after the page is interactive.

​

Trying the Tools

​

What Is Not Here Yet

• Checkout. No tool opens or completes checkout. Payment stays a human step, on the page.
• Custom domains. Whitelabel domains get no tools while the origin trial is per-origin.
• Catering and Pay at Table. Neither flow is exposed; the tools cover Delivery, Pickup and InStore ordering.
• Order history. There is no tool for past orders or order status.

For an agent that is not in the customer’s browser, use the MCP endpoint instead — the same menu shaping over HTTP, with its own tool names and a cart rather than the page’s basket.