Token-Oriented Object Notation (TOON)

Skill by ara.so — Daily 2026 Skills collection.

TOON is a compact, human-readable encoding of the JSON data model that minimizes tokens for LLM input. It combines YAML-style indentation for nested objects with CSV-style tabular layout for uniform arrays, achieving ~40% token reduction while maintaining or improving LLM comprehension accuracy.

Installation

# npm
npm install @toon-format/toon

# pnpm
pnpm add @toon-format/toon

# yarn
yarn add @toon-format/toon

CLI

# Install globally
npm install -g @toon-format/toon

# Convert JSON file to TOON
toon encode input.json
toon encode input.json -o output.toon

# Convert TOON back to JSON
toon decode input.toon
toon decode input.toon -o output.json

# Pipe support
cat data.json | toon encode
cat data.toon | toon decode

# Pretty-print JSON output
toon decode input.toon --pretty

# Show token count comparison
toon encode input.json --stats

Core API

encode / stringify

import { encode, decode } from '@toon-format/toon';

// Basic encoding (JSON → TOON string)
const data = {
  context: {
    task: 'Our favorite hikes together',
    location: 'Boulder',
    season: 'spring_2025',
  },
  friends: ['ana', 'luis', 'sam'],
  hikes: [
    { id: 1, name: 'Blue Lake Trail', distanceKm: 7.5, elevationGain: 320, companion: 'ana', wasSunny: true },
    { id: 2, name: 'Ridge Overlook', distanceKm: 9.2, elevationGain: 540, companion: 'luis', wasSunny: false },
    { id: 3, name: 'Wildflower Loop', distanceKm: 5.1, elevationGain: 180, companion: 'sam', wasSunny: true },
  ],
};

const toon = encode(data);
console.log(toon);
// context:
//   task: Our favorite hikes together
//   location: Boulder
//   season: spring_2025
// friends[3]: ana,luis,sam
// hikes[3]{id,name,distanceKm,elevationGain,companion,wasSunny}:
//   1,Blue Lake Trail,7.5,320,ana,true
//   2,Ridge Overlook,9.2,540,luis,false
//   3,Wildflower Loop,5.1,180,sam,true

decode / parse

import { decode } from '@toon-format/toon';

const toonString = `
context:
  task: Our favorite hikes together
  location: Boulder
friends[2]: ana,luis
hikes[2]{id,name,distanceKm}:
  1,Blue Lake Trail,7.5
  2,Ridge Overlook,9.2
`;

const parsed = decode(toonString);
// Returns the original JavaScript object
console.log(parsed.hikes[0].name); // 'Blue Lake Trail'

Encoding options

import { encode } from '@toon-format/toon';

const toon = encode(data, {
  // Force all arrays to tabular format (default: auto-detect uniform arrays)
  tabular: 'always',

  // Never use tabular format
  // tabular: 'never',

  // Indent size for nested objects (default: 2)
  indent: 2,

  // Quote strings that contain special characters (default: auto)
  quoting: 'auto',
});

Format Overview

Primitive scalars

TOON encodes scalars the same way as YAML — unquoted when unambiguous: