JSON to TOON Converter

Convert JSON files to TOON format and reduce your LLM API token usage. See exactly how many tokens you save with each conversion.

🎯 What is TOON?

TOON is a token-optimized format for representing structured data in LLM prompts. It uses significantly fewer tokens than JSON while maintaining readability and structure, resulting in:

Lower API costs - Fewer tokens = less money spent on API calls
Larger context windows - Fit more data in the same token budget
Better performance - Less data for the LLM to process

✨ Features

Bidirectional Conversion: Convert JSON ↔ TOON seamlessly
Token Counting: Accurate token counting using Claude Sonnet 4.5 tokenizer
Savings Visualization: See exactly how many tokens and what percentage you save
Batch Operations: Convert or revert all files in your workspace at once
File Replacement: Converts files in-place (JSON → TOON or TOON → JSON)
Keyboard Shortcut: Quick conversion with Ctrl+Shift+T (or Cmd+Shift+T on Mac)

📦 Installation

From VS Code Marketplace

Open VS Code
Go to Extensions (Ctrl+Shift+X)
Search for "JSON to TOON Converter"
Click Install

From VSIX File

Download the .vsix file from releases
Open VS Code Extensions (Ctrl+Shift+X)
Click "..." menu → "Install from VSIX..."
Select the downloaded file

🚀 Usage

Convert Single File (JSON → TOON)

Open any .json file in VS Code
Right-click in the editor or file explorer
Select "Convert JSON to TOON"
Your file is converted to .toon and the original .json is removed

Or use keyboard shortcut: Ctrl+Shift+T (Windows/Linux) or Cmd+Shift+T (macOS)

Convert All Files (JSON → TOON)

Open Command Palette (Ctrl+Shift+P or Cmd+Shift+P)
Type "Convert All JSON Files to TOON"
All .json files in your workspace are converted to .toon

Revert Single File (TOON → JSON)

Open any .toon file in VS Code
Right-click in the editor or file explorer
Select "Revert TOON to JSON"
Your file is converted back to .json and the .toon file is removed

Revert All Files (TOON → JSON)

Open Command Palette (Ctrl+Shift+P or Cmd+Shift+P)
Type "Revert All TOON Files to JSON"
All .toon files in your workspace are converted back to .json

📊 Real-World Example

Let's compare a typical API response with user data:

Input JSON (487 tokens):

{
  "users": [
    {
      "id": "usr_1234567890",
      "username": "john.doe",
      "email": "john.doe@example.com",
      "role": "admin",
      "is_active": true,
      "login_count": 156
    },
    {
      "id": "usr_0987654321",
      "username": "jane.smith",
      "email": "jane.smith@example.com",
      "role": "user",
      "is_active": true,
      "login_count": 89
    },
    {
      "id": "usr_5555555555",
      "username": "bob.wilson",
      "email": "bob.wilson@example.com",
      "role": "user",
      "is_active": false,
      "login_count": 12
    }
  ],
  "pagination": {
    "current_page": 1,
    "total_pages": 10,
    "per_page": 20,
    "total_items": 200
  }
}

Output TOON (243 tokens):

users[3]{id,username,email,role,is_active,login_count}:
  usr_1234567890,john.doe,john.doe@example.com,admin,true,156
  usr_0987654321,jane.smith,jane.smith@example.com,user,true,89
  usr_5555555555,bob.wilson,bob.wilson@example.com,user,false,12
pagination:
  current_page: 1
  total_pages: 10
  per_page: 20
  total_items: 200

Result: ✨ Converted 1 file to TOON! 🎉 Total saved: 244 tokens (50.1%)

Notice how TOON's compact table syntax users[3]{id,username,email,role,is_active,login_count}: eliminates repetitive field names and brackets, saving tokens while maintaining perfect readability!

💰 Cost Impact

With Claude Sonnet 4.5 pricing ($3 per 1M input tokens):

1,000 API calls: Save $0.73
10,000 API calls: Save $7.32
100,000 API calls: Save $73.20
1M API calls: Save $732.00

The savings add up quickly, especially for high-volume applications!

🤖 Using TOON Files with LLMs

To maximize your token savings, configure your AI coding assistants to use TOON files instead of JSON:

For Claude (via .clinerules or .cursorrules)

Add this instruction to your .clinerules or .cursorrules file:

When working with structured data files in this project:
- Always use .toon files instead of .json files for reading data
- TOON format is more token-efficient than JSON
- Parse TOON files using the @toon-format/toon library

For GitHub Copilot

Add this to your workspace settings (.vscode/settings.json):

{
  "github.copilot.advanced": {
    "inlineSuggestCount": 3,
    "instructions": [
      "When reading structured data, prefer .toon files over .json files to save tokens",
      "Use @toon-format/toon library to parse TOON format files"
    ]
  }
}

General LLM Instructions

Include this in your project documentation or system prompts:

This project uses TOON format (.toon files) for structured data instead of JSON to reduce token usage.
Always read from .toon files when available. Use the decode() function from @toon-format/toon to parse them.

⚙️ Configuration

Configure the extension through VS Code settings:

{
  "jsonToToon.showStats": true // Set to false to hide token statistics
}

🔧 Requirements

VS Code 1.96.0 or higher
The extension works out of the box - no additional dependencies needed

📝 Commands

Command	Description
`Convert JSON to TOON`	Convert single JSON file to TOON format
`Convert All JSON Files to TOON`	Convert all JSON files in workspace to TOON
`Revert TOON to JSON`	Convert single TOON file back to JSON
`Revert All TOON Files to JSON`	Convert all TOON files in workspace back to JSON

🐛 Troubleshooting

Extension Not Working

Ensure you have a .json or .toon file open
Check VS Code version (must be 1.96.0+)
Reload VS Code: Ctrl+Shift+P → "Reload Window"

Token Counting Issues

The extension uses js-tiktoken with Claude Sonnet 4.5 tokenizer
Falls back to estimation (chars/4) if tokenizer fails
Check Output panel: "JSON to TOON" for detailed logs

Conversion Errors

Verify JSON is valid using VS Code's built-in JSON validator
Check the Output panel for detailed error messages
Ensure files are not read-only

🛠️ Development

Building from Source

# Clone repository
git clone https://github.com/patryk-penczek/json-to-toon-converter.git
cd json-to-toon-converter

# Install dependencies
npm install

# Compile TypeScript
npm run compile

# Test in Extension Development Host
# Press F5 in VS Code

🤝 Contributing

Contributions are welcome! Please:

Fork the repository
Create a feature branch
Make your changes
Submit a pull request

📄 License

MIT License - see LICENSE file for details

🔗 Links

💖 Support

If you find this extension helpful:

⭐ Star the repository
🐛 Report bugs and issues
💡 Suggest new features
📢 Share with others

Save tokens, save money! Made for the LLM community 🚀

JSON to TOON

Patryk Penczek