js-notepad: A Scriptable Notepad with Built-in MCP Server for Claude Code

js-notepad is a scriptable notepad application designed to work alongside VS Code while using Claude Code. It serves as a companion tool for coding workflows, built entirely with Claude Code assistance.

Key Features and Use Cases

The developer uses js-notepad side-by-side with VS Code during Claude Code sessions for several specific purposes:

• Reviewing documentation – Markdown renders live with Mermaid diagram support, and HTML mockups preview in a built-in browser tab.
• Tracking work – Quick todos and notes can be created without leaving the workspace.
• Monitoring changes – Multiple tab groups with navigation panels allow browsing project files and reviewing what Claude has implemented.

Technical Implementation

The application includes several technical components:

• Built-in MCP server – This enables Claude Code to read/write pages, execute scripts, create todos, and push results directly into the application.
• Monaco Editor – The same editor engine used by VS Code.
• Grid editor – For working with JSON and CSV files.
• Notebook and todo editors – Dedicated interfaces for different content types.
• PDF viewer – Built-in PDF viewing capability.
• JavaScript/TypeScript scripting – With full Node.js access for custom functionality.

The tool is free, open source, and currently available for Windows. The source code is hosted on GitHub at github.com/andriy-viyatyk/js-notepad.