What's WebMCP?
Understanding MCP and WebMCP — the standards powering AI agent connectivity
What is MCP?
MCP (Model Context Protocol) is an open-source standard for connecting AI applications to external systems. Created by Anthropic in November 2024, it provides a universal way for AI apps like Claude, ChatGPT, and VS Code to access data sources, tools, and workflows.
How MCP Works
MCP follows a client-server architecture. An MCP host (like Claude Desktop or VS Code) creates MCP clients that connect to MCP servers. Communication uses JSON-RPC 2.0 over two transport types: STDIO for local servers and Streamable HTTP for remote servers.
The AI application that coordinates and manages one or multiple MCP clients (e.g., Claude Desktop, VS Code)
A component that maintains a connection to an MCP server and obtains context for the host
A program that provides context — tools, resources, and prompts — to MCP clients
Core Primitives
Executable functions that AI models can invoke (e.g., search, calculate, query databases)
Data sources that provide context to AI models (e.g., files, database records, API responses)
Reusable prompt templates that servers can expose to clients for specific workflows
What MCP Enables
- AI assistants accessing your Google Calendar and Notion for personalized help
- Claude Code generating entire web apps from Figma designs
- Enterprise chatbots connecting to multiple databases across an organization
- AI models creating 3D designs on Blender and printing them on a 3D printer
What is WebMCP?
WebMCP (Web Model Context Protocol) is a W3C Community Group standard that enables browsers to expose structured tools to AI agents through the navigator.modelContext API. Jointly developed by Google and Microsoft, it was released as an early preview in Chrome 146 in February 2026.
Two Complementary APIs
HTML-based tool registration using form attributes. Simple and requires no JavaScript.
JavaScript-based dynamic tool registration with full programmatic control via navigator.modelContext.registerTool().
Security-First Design
- Human-in-the-Loop: Core design principle requiring user confirmation for sensitive operations.
- Read-Only Hints: Tools can be marked as read-only to bypass confirmation for query operations.
- Permission Model: Browser-mediated consent flows similar to existing web platform APIs (like location or camera access).
MCP vs WebMCP
MCP and WebMCP are complementary protocols. MCP connects AI agents to backend services; WebMCP connects them to browser-based interfaces.
| Feature | MCP | WebMCP |
|---|---|---|
| Environment | Server-side / cross-platform | Browser-native / client-side |
| Protocol | JSON-RPC 2.0 | postMessage (browser) |
| Authentication | Custom per-server | Inherits web auth (SSO, cookies, RBAC) |
| Best for | Headless API operations, CLI agents, desktop AI assistants | In-browser UI interactions, web app automation, context-sensitive tools |
| Developed by | Anthropic (open-source) | Google & Microsoft (W3C Community Group) |
Code Examples
MCP Server Tool (JSON-RPC)
// MCP Server — defining a tool
{
"name": "search_flights",
"description": "Search available flights between airports",
"inputSchema": {
"type": "object",
"properties": {
"origin": { "type": "string", "description": "Origin airport code (IATA)" },
"destination": { "type": "string", "description": "Destination airport code" },
"date": { "type": "string", "format": "date" }
},
"required": ["origin", "destination", "date"]
}
}WebMCP Imperative API (Browser)
// WebMCP — browser-native tool registration
navigator.modelContext.registerTool({
name: "searchFlights",
description: "Search available flights",
inputSchema: {
type: "object",
properties: {
origin: { type: "string", pattern: "^[A-Z]{3}$" },
destination: { type: "string", pattern: "^[A-Z]{3}$" },
date: { type: "string", pattern: "^\\d{4}-\\d{2}-\\d{2}$" }
},
required: ["origin", "destination", "date"]
},
async execute({ origin, destination, date }) {
const results = await flightAPI.search({ origin, destination, date });
return {
content: [{ type: "text", text: JSON.stringify(results) }]
};
}
});How webmcp.land Fits In
webmcp.land is a discovery platform for MCP and WebMCP services. Users register their server endpoints, and the platform discovers, indexes, and exposes their tools so others can search by use case — like finding a flight booking tool or a database query service.
- 1Register your MCP or WebMCP endpoint URL
- 2The platform discovers and indexes your tools and capabilities
- 3Others search by use case to find and connect to your services