@web-axag/shim

A document.modelContext for browsers that don't have one yet, so code written against WebMCP runs unchanged.

npm install @web-axag/shim

import { installShim } from '@web-axag/shim';

installShim(); // no-op where the browser has its own implementation

Then register as usual — @web-axag/webmcp and the framework bindings find the shim exactly as they find a native implementation:

registerManifest(tools, { signal: route.signal, handlers });

What it is, and isn't

It implements the part of the draft a page calls: registerTool(tool, { signal }), with abort unregistering. It keeps the registered tools somewhere a bridge or an inspector can read them.

Installing it connects no agent. It is the socket a connection plugs into — @web-axag/bridge is one such connection.

Reading the registry

import { getShimRegistry } from '@web-axag/shim';

const registry = getShimRegistry();
registry?.listTools();                       // what is registered right now
registry?.subscribe(tools => render(tools));  // called whenever that changes
await registry?.callTool('order_track', { order_id: 'o1' });

Under 2 KB gzipped, with no dependencies: this is the one piece that ships on every page.