WebMCP — Make Any Website Agent-Ready MCP server

webmcp-sdk

AI Disclosure: This README was written with AI assistance and reviewed for accuracy.

The developer toolkit for W3C WebMCP -- the standard shipping in Chrome 146

Make any website agent-ready in 10 minutes. Built for navigator.modelContext.

✅ Google + W3C Validated — Why Now Is the Moment

March 2026 update: Google shipped WebMCP in Chrome 146 Canary. Google, Microsoft, and W3C co-authored the specification. This is not a startup experiment — it's Big Tech stamping a new web standard.

Why Now?

• Chrome 146 Canary shipped WebMCP in February 2026. Broad stable release expected mid-to-late 2026.
• Google + Microsoft + W3C co-authored the spec. Three institutions that don't move together unless something matters.
• Real implementations are live. LocalPlate (restaurant booking) shipped WebMCP on Astro. Existing HTML form sites become agent-compatible with minimal changes.
• The adoption curve is early. Developers who ship WebMCP integrations now own the search results, the tutorials, and the mindshare when the stable release lands.
• webmcp-sdk is the only TypeScript-first implementation toolkit. We built it before the spec finalized and we maintain it as the standard evolves.

If you're building for the agentic web, the window to establish yourself as an early implementer is right now.

Why webmcp-sdk?

Google and Microsoft co-authored the W3C WebMCP specification. The standard shipped in Chrome 146 Canary (February 2026). We built the implementation toolkit.

The raw navigator.modelContext API is low-level. webmcp-sdk gives developers a TypeScript-first, production-ready layer on top of it:

• Zero to agent-ready in 10 minutes -- declarative HTML attributes or imperative JavaScript
• Security middleware built in -- rate limiting, input sanitization, audit logging
• React hooks -- useWebMCPTool() registers on mount, cleans up on unmount
• Testing utilities -- mock browser context, test runner, quality scorer
• agentwallet-sdk compatible -- plug in x402 agent payments with 2 lines of code
• 50/50 compatibility tests passing on Chrome 146 Canary

If you are building for the agentic web, this is the toolkit.

Quick Install

npm i webmcp-sdk

Fastest Path to First Verified Success

import { createKit, defineTool } from 'webmcp-sdk';

const kit = createKit({ prefix: 'demo' });

kit.register(defineTool(
  'hello',
  'Return a greeting for the supplied name.',
  {
    type: 'object',
    properties: {
      name: { type: 'string', description: 'Name to greet' }
    },
    required: ['name']
  },
  async ({ name }) => {
    return { message: `Hello, ${name}!` };
  }
));

const result = await kit.invoke('demo.hello', { name: 'Bill' });
console.log(result);
// { message: 'Hello, Bill!' }

This works in Node or tests with no browser setup.

When navigator.modelContext is available in the browser, kit.register(...) also registers the tool there automatically. There is no separate init() step.

Browser Registration

Canonical docs and example in this repo:

• docs/browser-hello-quickstart.md
• examples/browser-hello/

import { createKit, defineTool } from 'webmcp-sdk';

const kit = createKit({ prefix: 'myshop' });

Shortened. The full README is on GitHub.