Observed arrival · 2026-09-18
WebMCP: Tools for AI Agents Inside the Browser
A technical proposal and implementation guide for exposing a website’s client-side actions to AI browser agents through document.modelContext.
- For
- Web developers building agent-accessible browser applications
- Worth noticing
- The proposed interface exposes tools through document.modelContext and includes same-origin and Permissions Policy details.
Field notes
The proposed interface places agent-callable tools in the page’s client-side application state, with examples for registering tools, discovering them, and invoking them through document.modelContext. The page distinguishes this from server-side MCP by emphasizing execution in the user’s tab and describes cross-origin controls through Permissions Policy. It also supplies separate implementation paths for plain web code, React or Next.js, and a polyfill, plus an agent-readable setup prompt and an inspector link.
Observed signals
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