WebMCP
A labeled menu of actions for the agent in your browser.
Reality check
Early use with two big real-world users, ChatGPT's desktop browser and Shopify, while Chrome and Edge are still in trials.
How it works
More and more AI assistants work inside your browser, clicking and typing on the page for you. Today they mostly do it by looking: reading the page's code or a screenshot, guessing which box is "departure date," and hoping the "Book" button didn't move in last week's redesign.
WebMCP lets the site say it plainly. A page registers "tools" in JavaScript (document.modelContext.registerTool()) with a name, a plain-English description, the fields it expects and the function that does the work, or tags an existing form with two attributes, toolname and tooldescription. On a hair-salon site, the agent stops hunting for the calendar widget and calls book_appointment with a date, time and service. It all happens in your own tab and signed-in session, so you can watch and step in.
One caveat: a page's tool descriptions are text the AI reads, so a malicious site can try to trick the agent, and Chrome says the defence is the agent's job.
Who's behind it
Microsoft and Google proposed it together in August 2025; the W3C's Web Machine Learning community group took it up that September, with editors from both companies. The current text is a draft dated October 9, 2026 that says plainly it is "not a W3C Standard."
Chrome has been testing it in a time-limited "origin trial" (Chrome 149-156) since May 2026; on September 28 Google asked to extend the trial to Chrome 162 because feedback is still changing the API, so there's no ship date. Edge runs its own trial (since Edge 150, through March 30, 2027) and calls it "ready for testing."
ChatGPT's desktop browser calls these "site tools" automatically, and Shopify puts WebMCP tools on every standard storefront, including a checkout tool that only completes after the buyer confirms. Safari's team opposes it and Firefox is neutral.
Neighbours
MCP servers serve agents that never load your page, and computer-use agents that read the screen remain the fallback. A related layer, MCP Apps (not covered here yet), goes the other way: it lets an MCP server ship interactive UI into the agent's chat.