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MCP-B

lastmod 2025-07-11created 2025-07-111 edits

Browser-native AI automation protocol

About

  • MCP-B: a browser-native AI automation protocol
  • A browser context protocol that lets AI automate 1,000x faster and more accurately by accessing a website's API directly, instead of the usual screen-capture-and-click approach
  • Adding only about 50 lines of code enables AI integration right away using the site's own authentication, without separate OAuth, API keys, or complex configuration
  • Uses the browser session and existing authentication system, so it works immediately without new authentication or permission setup, and fully respects each web app's API security policy
  • Through the extension, AI assistants can query data and perform tasks directly across multiple tabs and apps, with dramatically better performance (execution within a few ms) and reliability than existing automation
  • Because it is structured API access, it is free from problems with UI changes, screenshot errors, and managing complex selectors. Both installation and use are very simple

MCP-B overview

  • MCP-B (Machine Context Protocol for Browsers) is a model context protocol for browsers, providing a standard for controlling and interacting with the browser environment in a way similar to AI-based terminal automation
  • The protocol clearly defines communication between the browser and the AI engine, structuring various kinds of automation and model interaction

How it differs from existing approaches

  • Traditional browser automation: screenshot analysis, clicking elements, fragile to UI changes, slow and unstable (10–20 seconds and $4–5 per task)
  • Existing MCP approach: requires API keys and complex authentication, high barrier to initial setup
  • MCP-B: uses the browser session, direct API access, works immediately without complex authentication or configuration

Core principles and architecture

  • Per-tab MCP server: each web app runs its own TypeScript-based MCP server (in-memory transport, reusing existing cookie/JWT authentication)
  • MCP-B extension: Chrome/Edge/Firefox extension (a content script communicates with the tab server via postMessage), unifying the tools and APIs of all tabs in one place
  • AI assistant integration: browser automation through MCP-B from the Native Bridge and various clients (Claude Desktop, Cursor IDE, etc.)

Usage and deployment

  • Developers: 1) install the package 2) add the MCP server code 3) deploy → no separate API keys, OAuth, or complex configuration needed
  • Users: install the extension and use it right away; automation works immediately with just AI configuration

Practical advantages

  • Authentication: uses existing website login and session information as is, no OAuth 2.1 or separate authentication needed
  • Performance: tasks complete in milliseconds via direct API calls (10,000x improvement over existing approaches)
  • Security: runs inside the application, fully complying with existing access control and permission policies
  • Scalability: multiple web apps, tabs, and AI tools can be managed together through MCP-B
  • Setup: ready for automation with only about 50 lines of code

See also

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