Friday, 21 November 2025

TOON: The Future of Structured Data for AI - A Simpler, Lighter, Human-Friendly Alternative to JSON

Standard


For more than a decade, JSON has been the backbone of web APIs. It’s everywhere powering apps, microservices, logs, configs, and data pipelines. But as we enter a world dominated by AI agents, LLM workflows, and token-optimized prompts, JSON is starting to show its age.

Today’s AI systems don’t just consume data ; they interpret it, reason with it, and generate new structures from it.

Yet JSON, with its endless braces, commas, and quotes, wasn’t built for that kind of work.

So a new idea has emerged:

TOON : Token-Oriented Object Notation

A compact, human-readable, AI-friendly alternative to JSON that reduces token cost, improves model understanding, and simplifies structured prompt design.

And honestly?
It’s one of the most refreshing innovations in AI tooling I’ve seen in years.

The Problem with JSON in AI Workflows

Let’s be fair JSON is excellent for machines.
But for humans designing structured prompts, tool schemas, agent configs, and reasoning structures, JSON becomes:

  • Too verbose
  • Hard to read
  • Token-inefficient
  • Not friendly for mixing text + structure + examples
  • Difficult to reference or reuse

Consider this: every {, ", :, and , you include in JSON becomes a token when passed to a language model. That is wasted budget, wasted context window, and wasted clarity.

The freeCodeCamp article puts it elegantly:

“JSON’s punctuation and quotes create unnecessary token bloat that doesn’t help the model understand your structure.”

And when your prompts or agent configs grow into the hundreds of lines, you feel that bloat.

Which brings us to…

Enter TOON: Token-Oriented Object Notation

TOON is a new notation format designed precisely for AI systems especially LLMs. It aims to solve JSON’s weaknesses while keeping the same underlying data model.

According to the official TOON GitHub repository:

“TOON is a compact, human-readable encoding of the JSON data model designed for LLM prompts. It provides a lossless serialization of objects, arrays, and primitives but with far fewer tokens.”

So you get the best of both worlds:

  • JSON compatibility
  • Human-friendly syntax
  • LLM-optimized token efficiency

It’s like someone finally said:
“What if structured data didn’t have to look like a programming parse tree?”

TOON vs JSON: A Side-by-Side Look

JSON Example

{
  "users": [
    { "id": 1, "name": "Alice", "role": "admin" },
    { "id": 2, "name": "Bob", "role": "user" }
  ]
}

TOON Equivalent

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

Immediately you notice:

✔ No quotes
✔ No braces
✔ No commas between fields
✔ Cleaner structure
✔ Fewer tokens
✔ Easier for both humans and LLMs to interpret

This is the magic of TOON.

TOON is Not Just YAML or a Shorthand - It’s Purpose-Built for AI

People might ask:
“Is TOON just another YAML or HCL?”

Not at all.

TOON is designed with 3 AI-specific goals:

1. Minimize Token Count

JSON forces every key and value into quotes, every object into {}, and every list into [].
TOON eliminates most of that.

Why this matters:

  • LLM context windows are limited
  • Token cost affects your bill
  • Structured prompts can get huge (tool definitions, agent descriptions, memory, etc.)

TOON often reduces token usage by 30–60%, according to early tests.

2. Improve Model Parsing & Predictability

Models don’t “see” braces and commas the way developers do. They see tokens.

TOON’s cleaner syntax helps models:

  • Parse structure more reliably
  • Respect fields more consistently
  • Follow templates more accurately

This is especially useful for:

  • Function calling
  • Structured output enforcement
  • Agent workflows
  • Multi-turn reasoning setups

3. Make Prompts and Schemas Human-Readable

TOON is designed for the people actually building AI systems:

  • Prompt engineers
  • Data scientists
  • Product teams
  • LLM app developers
  • Multi-agent workflow designers

You can read TOON like a clean, modern DSL.

A Real-World Example: Defining Tools and Agents in TOON

JSON Tool Definition

{
  "name": "get_weather",
  "description": "Fetch weather by city name",
  "schema": {
    "type": "object",
    "properties": {
      "city": { "type": "string" }
    },
    "required": ["city"]
  }
}

TOON Equivalent

tool get_weather:
  description: Fetch weather by city name
  args{city:string!}

That’s it.

  • Cleaner
  • Easier to edit
  • Far fewer tokens
  • Still maps 1:1 to JSON

TOON Supports Deep Structures Too

JSON:

{
  "article": {
    "title": "AI in 2025",
    "tags": ["ai", "future", "trends"],
    "author": {
      "name": "Ravi",
      "followers": 5000
    }
  }
}

TOON:

article:
  title: AI in 2025
  tags[3]: ai,future,trends
  author:
    name: Ravi
    followers: 5000

It looks like a hybrid of:

  • JSON’s structure
  • CSV’s compactness
  • YAML’s simplicity

But behaves like token-optimized JSON under the hood.

Developer Experience: Using TOON in Your Apps

The official GitHub repo provides SDKs for:

✔ TypeScript / JavaScript

npm install @toon-format/toon

✔ Python

pip install python-toon

Convert JSON → TOON (CLI)

npx @toon-format/cli input.json -o output.toon

Convert TOON → JSON

npx @toon-format/cli input.toon -o output.json

You can integrate TOON anywhere you are already using:

  • JSON configs
  • AI prompts
  • LLM tool schemas
  • Agent definitions
  • Structured output templates

Where TOON Really Shines

1. AI tool calling

Cleaner schemas, fewer tokens, better consistency.

2. Multi-agent ecosystems

Easier to define agent roles, memory, context, and routing rules.

3. RAG pipelines

Structured metadata is more readable and cheaper to embed.

4. Workflow orchestration

Tasks, edges, and dependencies look like a proper DSL instead of a JSON jungle.

5. Prompt engineering at scale

Prompts become easier to maintain, version, document, and share.

Limitations of TOON (Honest Assessment)

The GitHub repo outlines some limitations:

  • Extremely irregular JSON might not compress well
  • Round-trip conversion should be tested for edge cases
  • JSON remains better for general web API interoperability
  • Tools and libraries are still maturing

TOON is not a replacement for JSON everywhere, it is a better tool for AI-specific use cases.

Final Thought: TOON is JSON for the AI Era

AI changes how we think about data.

And TOON feels like the first serialization format truly designed for the LLM age where:

  • Human readability
  • Token efficiency
  • Structured reasoning
  • Model-friendliness

…all matter just as much as machine parsing.

TOON is not a buzzword, it’s a practical, elegant evolution in how we express structured information to AI systems.

If you work with prompts, agents, or structured LLM outputs, TOON will feel like a breath of fresh air i.e  simple, compact, powerful.

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