Byakugan: Private, Open Source AI Text Checker

Check whether writing reads as AI, on your own machine, then improve how it reads. Free and open source.

Two ways to use it.

1. In your browser

A static web app. Paste your text and get a read on how AI-like it sounds, with a plain-language explanation, a grammar pass, and a check against your own documents for reuse. Everything runs in the page, and nothing you paste leaves the browser.

Run it locally:

cd site
npm install
npm run dev

2. Inside the AI you already use

A mcp server for your AI assistant (Claude Desktop, an IDE, any MCP client). It gives that AI a detection read plus the exact phrases that read as AI, so your own AI can check and rewrite your writing, on your machine.

For Claude Desktop, add this to claude_desktop_config.json and restart:

{
  "mcpServers": {
    "ai-checker": {
      "command": "npx",
      "args": ["-y", "@jayofemi/ai-checker"]
    }
  }
}

Claude Code users can install it as a plugin instead: /plugin marketplace add JayOfemi/byakugan, then /plugin install ai-checker@ai-checker.

Then tell your AI "use ai-checker to check this text" and paste what you want checked. Full setup, the tools, and how to verify it are in mcp/README.md.

What to expect

AI-text detection is a signal, not a verdict, and it is biased against non-native English writers. It is shown as a likelihood with its confidence, never a yes/no judgement. Stiff, even, stock-phrase-heavy writing reads high; varied, personal writing reads low. Use it on your own work.

Layout

• site/ - the browser checker, a static web app. See site/README.md.
• mcp/ - the MCP server and TypeScript library. See mcp/README.md.

Each folder is its own package with its own build. Node 22 (.nvmrc).

License

MIT. Copyright (c) 2026 Jay Ofemi.