WebMCP
web model context protocol, navigator.modelContext, web-mcpDefinition
The Web Model Context Protocol — a browser API, navigator.modelContext, through which a web page declares the things it can do as named, typed tools (find a flight, add to cart, file a ticket) so that an agent driving the browser calls them directly instead of reading the screen and guessing where to click
Proposed by engineers at Google and Microsoft and drafted in the W3C's Web Machine Learning Community Group, with Chrome shipping the API behind a flag in early 2026. It borrows MCP's idea — a tool has a name, a description and an input schema — but the page is the server: the tools are registered by the site's own JavaScript, run in the page with the user's session, and vanish when the tab closes. For a site that already has a design system, the tools are the same contracts as the components, stated once more for a different reader. A Community Group draft, not a Recommendation; the agent side of the API is what the browsers are still deciding.
The accessibility argument, run again for a new reader. A page that says what it is — semantic HTML, an accessible name on every control — already tells a screen reader what can be done; WebMCP says the same thing to an agent in the agent's own shape. The sites that did the first well will find the second short.