WebMCP — Discover and Use Website Tools

What is WebMCP

WebMCP is a browser API that lets websites expose JavaScript functions as structured tools for AI agents. Pages register tools via window.navigator.modelContext, each with a name, description, JSON Schema input, and an execute callback. Think of it as an MCP server running inside the web page itself.

Spec: https://github.com/webmachinelearning/webmcp

Detecting WebMCP Support

Before interacting with tools, check whether the current page supports WebMCP:

const supported = "modelContext" in window.navigator;

If false, the page does not expose WebMCP tools — fall back to DOM interaction or actuation.

Discovering Available Tools