WebMCP
The standard, documented against the specification
What the API actually looks like, where it stands, and what it does not replace. Every claim is sourced to the specification, the explainer or the Chrome documentation, and dated.
What WebMCP is, and what it is not
A browser API that lets a page hand an AI agent a list of named, typed functions instead of a DOM to guess at. Here is the shape of it, the state of it, and the honest case for building on it now.
7 sources · reviewed 30 September 2026
Registering WebMCP tools with JavaScript
Define a JavaScript tool with clear inputs, outputs and lifecycle behavior. Compare the evolving draft with the browser and assistant you actually test.
5 sources · reviewed 30 September 2026
The declarative API: tools from forms you already have
Chrome documents WebMCP form annotations. Review the attributes, keep the form usable and test validation and submission in your intended browser client.
5 sources · reviewed 30 September 2026
WebMCP in Chrome: setup, origin trial and tool testing
Flags, the origin trial, and the difference between the two. Plus how to confirm your tools registered, rather than assuming they did because the code ran.
6 sources · reviewed 30 September 2026
WebMCP versus MCP, raw APIs and browser automation
Four ways an agent can reach your product, what each costs you, and the one question that decides between them: who is holding the credential.
5 sources · reviewed 27 August 2026
The WebMCP security model, and the parts that are still open
Session-based access is a genuine improvement over handing an agent an API key. It is not a complete threat model, and the specification says so. What to rely on, what to gate, and what to tell a compliance officer.
5 sources · reviewed 27 August 2026
navigator.modelContext is deprecated. Move to document.modelContext
The specification relocated the API in July 2026 and Chrome 150 deprecated the old position while the origin trial still serves it. A short migration with a long tail of quiet breakage if you skip it.
4 sources · reviewed 27 August 2026
Shipping WebMCP before the browsers catch up
A polyfill provides document.modelContext where the browser does not, a React hook ties registration to component lifecycle, and a relay bridges page tools to desktop clients. What each is for, and where the seams are.
5 sources · reviewed 25 September 2026