VCN #39: Browser Tax — Instrument Your Site with WebMCP

Instrument your site browser side. The agent finally sees what the human sees. Agents pay a tax to use the web. They scrape DOM, infer affordances from labels, click buttons that don't surface in the accessibility tree, retry on errors that humans never notice. The tax is paid in latency, hallucination, and unreliability — and you pay it every time an agent touches your product. WebMCP is the inversion. You instrument the page once. The agent calls navigator.modelContext.registerTool({...}). Same DOM, two callers — humans see a button, agents see a tool. Calls inherit the browser session without separate auth. Chrome 146 Canary shipped early-preview in February 2026. Microsoft's NLWeb is the sibling proposal — NL queries over Schema.org structured data, and every NLWeb instance also acts…