TOON vs JSON: A New Data Format Optimized for LLMs

Table of Contents

1. Introduction
2. What is TOON (LLM Data Format)?
3. The Problem with JSON Data Format in LLMs
4. How TOON Solves This
5. TOON vs JSON Comparison
6. When Should You Use TOON?
7. When JSON is Still Better
8. Limitations of TOON
9. Is TOON the Future?
10. Conclusion

Introduction

Large Language Models like GPT models are powerful, but they come with a cost—tokens. Traditional formats like JSON often include repetitive and verbose syntax, increasing both cost and inefficiency.

A new format called TOON (Token-Oriented Object Notation) aims to solve this by reducing redundancy and optimizing data representation specifically for LLMs.

In this blog, we’ll explore what TOON is, how it compares to JSON, and when you should consider using it.

1. What is TOON (LLM Data Format)?

TOON (Token-Oriented Object Notation) is an experimental data format designed to minimize token usage when working with LLMs.

Key Idea:

• Define structure once
• Avoid repeating keys
• Represent data in a compact, table-like format

2. The Problem with JSON Data Format in LLMs

While JSON is widely used, it has some limitations in AI workflows:

{ "id": 1, "name": "Alice" }
{ "id": 2, "name": "Bob" }

Token Inefficiency

• Same keys repeated multiple times
• More tokens → higher cost
• Not optimized for LLM thinking

3. How TOON Solves This

TOON Example:

users[2]{id,name}:
1,Alice
2,Bob

Benefits:

• Structure defined once
• Compact representation
• Lower token usage

4. TOON vs JSON Comparison

5. When Should You Use TOON?

Use TOON when:

• You are sending large structured data to LLMs
• Token cost is important
• Data has repeated structure (tables, logs, etc.)

6. When JSON is Still Better

Stick with JSON when:

• Building APIs (e.g., with FastAPI)
• Need validation (schemas, Pydantic)
• Storing data in databases
• Reliability is critical

7. Limitations of TOON

• Not a standard yet
• No widespread parser support
• LLMs are not heavily trained on it
• Complex nested structures can be tricky

8. Is TOON the Future?

TOON introduces an important idea:

“Data formats for AI should be optimized for tokens, not just structure.”

While it’s not ready to replace JSON, it opens the door for:

• Token-efficient data formats
• Smarter LLM communication
• Cost-optimized AI systems

Conclusion

TOON is an exciting step toward LLM-native data formats, but it’s still experimental.

Use TOON for efficiency experiments

Use JSON for real-world systems