simple_toon

Overview

TOON is a compact, human-readable format designed to minimize token usage when sending structured data to Large Language Models. simple_toon provides seamless conversion between JSON and TOON formats, achieving 30-60% token reduction while maintaining lossless round-trip conversion.

Part of the Simple Eiffel ecosystem.

Format Comparison

Simple Objects

{
  "name": "Alice",
  "age": 30,
  "active": true
}

name: Alice
age: 30
active: true

Tabular Arrays

[
  {"sku": "A1", "name": "Widget", "price": 9.99},
  {"sku": "B2", "name": "Gadget", "price": 14.50}
]

[2]{sku,name,price}:
  A1,Widget,9.99
  B2,Gadget,14.5

Quick Start

Installation

1. Set the environment variable:

   export SIMPLE_EIFFEL=/d/prod

2. Add to your ECF file:

   <library name="simple_toon" location="$SIMPLE_EIFFEL/simple_toon/simple_toon.ecf"/>

Encode & Decode

local
    toon: SIMPLE_TOON
    json: SIMPLE_JSON
    value: SIMPLE_JSON_VALUE
    toon_text, json_text: STRING_32
do
    create toon.make
    create json

    -- Encode JSON to TOON
    value := json.parse ("{%"name%": %"Alice%", %"age%": 30}")
    toon_text := toon.encode (value)
    -- Result: "name: Alice%Nage: 30"

    -- Decode TOON to JSON
    value := toon.decode ("name: Bob%Nage: 25")
    json_text := value.to_json_string
    -- Result: {"name":"Bob","age":25}

    -- Check compression ratio
    print ("Compression: " + (toon.compression_ratio (value) * 100).out + "%%")
end

Decimal Precision

simple_toon integrates with simple_decimal and simple_json's decimal support to ensure exact number representation without floating-point artifacts.

-- Using put_real
obj.put_real (19.99, "price")
-- JSON output: {"price": 19.989999999999998}
-- TOON output: price: 19.989999999999998

-- Using put_decimal
create price.make ("19.99")
obj.put_decimal (price, "price")
-- JSON output: {"price": 19.99}
-- TOON output: price: 19.99

For financial data or any values requiring exact decimal representation, use put_decimal with SIMPLE_DECIMAL instead of put_real.

Key Features

API Reference

Configuration Options

TOON Syntax Reference

key: value
nested:
  inner_key: inner_value

[3]: red,green,blue

[2]{sku,qty,price}:
  A1,10,9.99
  B2,20,14.50

[2]:
  - id: 1
    name: Alice
  - id: 2
    name: Bob

When to Use TOON

Resources

• GitHub Repository
• TOON Specification
• TOON Format Website