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The MCP-B Extension is a Chrome extension that collects WebMCP tools from all open tabs and makes them available to AI agents.

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Installation

Install MCP-B Extension

Get the extension from the Chrome Web Store

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How It Works

The extension:
  • Discovers tools registered via navigator.modelContext on any tab
  • Aggregates tools from all open tabs
  • Provides built-in agents for common tasks
  • Bridges tools to local MCP clients (Claude Desktop, Claude Code, etc.)

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Built-in Agents

The extension includes specialized agents:

Userscript Engineer

Build custom scripts to enhance websites

WebMCP Server

Turn websites into AI-accessible tools

Browsing Agent

Navigate and inspect web pages

Chat Companion

Ask questions without automation

Understanding Agents

Learn about each agent and when to use them

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Connecting to Local MCP Clients

Bridge your browser tools to Claude Desktop, Claude Code, or other MCP clients:
1

Install the native server

npm install -g @mcp-b/native-server
2

Start the server

@mcp-b/native-server
3

Configure your MCP client

Add to your MCP client config (e.g., ~/.config/claude/mcp.json):
{
  "mcpServers": {
    "webmcp": {
      "type": "streamable-http",
      "url": "http://127.0.0.1:12306/mcp"
    }
  }
}

Native Host Setup

Complete setup guide for local MCP client integration

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Creating Custom Tools

Use userscripts to add tools to any website:

Managing Userscripts

Create and manage custom WebMCP tools

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Privacy & Security

  • The extension only accesses tools that websites explicitly register
  • Tools are scoped by domain
  • Native server listens on localhost only
  • No data is sent to external servers

Extension Architecture

Technical details about how the extension works