WebMCP read-only tool surface
Registered three read-only, agent-callable WebMCP tools behind Chrome's origin trial — pure progressive enhancement, removable in one step, and consumed by approximately nothing.
The live pages now register three read-only WebMCP tools — describe_site, get_recent_writing, and search_content — backed by a single static JSON index. They’re layered on as progressive enhancement: the site renders and behaves identically with the whole feature deleted, and does so in exactly one step.
The hypothesis, and where it broke
Going in, I assumed Chrome might return the API undefined even with a valid token, that document.modelContext was the new surface and navigator the deprecated one, and that Chrome would validate the declared input schema. Measured against Chrome 150 on the live origin trial, three of those were wrong.
The API works, the two surfaces are the same object, and Chrome does not validate the schema — which means the input-clamping guards in the tool handlers are load-bearing validation, not decoration.
No consumption claimed
Registration and execution were driven through devtools against the real API, not by an agent. The origin-trial token expires 2026-11-17, after which Chrome ignores it and the tools silently stop registering — a harmless no-op. This is the kind of result this site exists to produce: shipped it, measured it, learned something specific, and it moved no metric anyone would notice.