Webmcp Setup

WebMCP Project Setup

Before writing code

Fetch live docs:

1. Fetch https://webmachinelearning.github.io/webmcp/ — the W3C Community Group draft report, which is the normative spec for navigator.modelContext. Start here, not with vendor docs.
2. Fetch https://developer.chrome.com/docs/ai/webmcp for Chrome's implementation notes and API overview.
3. Web-search site:github.com mcp-b polyfill README for polyfill installation and quickstart.
4. Web-search webmcp chrome flag enable for current browser flag names and version requirements — these change per milestone.
5. Web-search site:chromestatus.com webmcp for feature status and shipping milestones.

Standards status: WebMCP is a W3C Community Group Draft Report hosted by the Web Machine Learning CG — it is not a W3C Standard and is not on the W3C Standards Track. Chrome is the reference implementation; other engines have participated in discussion without shipping. Plan for the API surface to move, keep the polyfill path viable, and re-check browser support rather than assuming it broadened.

Conceptual Architecture

What Setup Involves

WebMCP project setup prepares a website to expose tools to AI agents:

1. Enable browser support — Chrome 146+ Canary with the WebMCP for Testing flag, or install the MCP-B polyfill
2. Install polyfill (if needed) — mcp-b packages for vanilla JS or React
3. Scaffold tool registration — create the entry point where tools are registered via navigator.modelContext.registerTool()
4. Configure development environment — set up testing with AI agents

Project Structure (Vanilla JS)

my-webmcp-site/
├── src/
│   ├── webmcp/
│   │   ├── tools.js              # Tool definitions and registration
│   │   ├── schemas.js            # JSON Schemas for tool inputs
│   │   └── interactions.js       # User interaction handlers
│   ├── index.html                # Page with optional declarative form attributes
│   └── app.js                    # Main application entry
├── package.json
└── tests/
    └── webmcp.test.js

Project Structure (React + MCP-B)

my-webmcp-react-app/
├── src/
│   ├── webmcp/
│   │   ├── tools.ts              # Tool definitions
│   │   ├── schemas.ts            # JSON Schemas
│   │   ├── McpProvider.tsx        # MCP-B React provider/hooks wrapper
│   │   └── interactions.ts       # User interaction logic
│   ├── App.tsx
│   └── index.tsx
├── package.json
├── tsconfig.json
└── tests/
    └── webmcp.test.tsx

Setup Decision Checklist

• Browser target — Native Chrome 146+ (flag-gated) or polyfill for broader support?
• Framework — Vanilla JS, React, Vue, or server-rendered HTML?
• API approach — Imperative (JS registerTool), Declarative (HTML attributes), or both?
• Tool scope — Which user journeys will be exposed as tools?
• Authentication — What user role is required before registering sensitive tools?
• Testing strategy — Which AI agents to test with (Gemini, Claude, etc.)?

Chrome Flag Setup

To enable native WebMCP in Chrome Canary:

1. Install Chrome 146+ Canary
2. Navigate to chrome://flags
3. Search for the WebMCP flag (name may change — search for it live)
4. Enable the flag and restart Chrome

MCP-B Polyfill Setup

For browsers without native WebMCP, the MCP-B polyfill provides the same API surface. Fetch the README for exact installation commands, as packages and APIs may have changed.

Best Practices

• Start with one or two simple read-only tools before adding transactional ones
• Use the polyfill for development even if targeting native Chrome — it works everywhere
• Register tools after the page has loaded and the user is authenticated
• Group related tools logically (all cart tools together, all search tools together)
• Test tool discovery with at least one AI agent before going to production

Fetch the latest Chrome blog post and MCP-B README for exact commands, package names, and API patterns before scaffolding.