LLM Integration

Overview

TOON is designed specifically for LLM input. This guide covers strategies, prompting techniques, and validation approaches to get the most out of TOON format when working with Large Language Models.

Why TOON for LLMs?

TOON provides three key advantages for LLM input:

Token Efficiency

~40% fewer tokens than JSON while maintaining lossless representation.

LLM-Friendly Structure

Explicit length declarations [N] and field headers {fields} improve parsing accuracy.

Human Readability

YAML-like indentation and CSV-style tables are familiar and easy to verify.

Basic Integration

Simple Data Encoding

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

const userData = {
  users: [
    { id: 1, name: 'Alice', role: 'admin', active: true },
    { id: 2, name: 'Bob', role: 'user', active: true },
    { id: 3, name: 'Carol', role: 'user', active: false }
  ]
}

// Encode with tab delimiter for maximum token efficiency
const toonData = encode(userData, { delimiter: DELIMITERS.tab })

// Include in LLM prompt
const prompt = `
Here is user data:

\`\`\`toon
${toonData}
\`\`\`

How many active users are there?
`

const response = await llm.complete(prompt)

Showing Format Instead of Describing

LLMs understand TOON naturally when they see examples:

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

const exampleData = {
  products: [
    { id: 1, name: 'Widget', price: 29.99, inStock: true },
    { id: 2, name: 'Gadget', price: 19.99, inStock: false }
  ]
}

const toon = encode(exampleData, { delimiter: DELIMITERS.tab })

const prompt = `
I'm providing data in TOON format (Token-Oriented Object Notation).

Example:
\`\`\`toon
${toon}
\`\`\`

Please analyze this product inventory and tell me which items need restocking.
`

Don’t explain TOON syntax in detail. LLMs parse it naturally from examples. The structure is self-documenting.

Optimal Formatting for LLMs

Use Tab Delimiters

Tab delimiters provide the best token efficiency:

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

const data = { /* your data */ }

// Tab delimiter: ~5-10% fewer tokens than comma
const toon = encode(data, { delimiter: DELIMITERS.tab })

Token Comparison:

Comma: users[2]{id,name,role}:\n  1,Alice,admin    (12 tokens)
Tab:   users[2]{id,name,role}:\n  1\tAlice\tadmin   (11 tokens)
Savings: ~8% reduction

Enable Key Folding

Collapse nested structures when appropriate:

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

const config = {
  server: {
    database: {
      connection: {
        host: 'localhost',
        port: 5432
      }
    }
  }
}

// Without key folding (more tokens)
const verbose = encode(config)
// server:
//   database:
//     connection:
//       host: localhost
//       port: 5432

// With key folding (fewer tokens)
const compact = encode(config, { keyFolding: 'safe' })
// server.database.connection:
//   host: localhost
//   port: 5432

Only use key folding for LLM input. If you need to decode the output back to JSON, use expandPaths: 'safe' to ensure lossless round-trips.

Prompting Strategies

Code Block Formatting

Always wrap TOON data in code blocks:

const prompt = `
Analyze this dataset:

\`\`\`toon
${toonData}
\`\`\`

Question: What is the average age of active users?
`

Why this works:

Models recognize structured data in code blocks
Preserves whitespace and formatting
Reduces ambiguity in parsing

Explicit Length Declarations

TOON’s [N] syntax helps LLMs validate completeness:

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

const data = {
  orders: [
    { id: 1, total: 100 },
    { id: 2, total: 200 },
    { id: 3, total: 150 }
  ]
}

const toon = encode(data)
// orders[3]{id,total}:  ← Length declaration helps LLM know to expect 3 items
//   1,100
//   2,200
//   3,150

LLMs can validate:

“Did I receive all 3 items?”
“Is the data complete or truncated?”

Field Headers for Structure

Field headers {id,name,role} act as schema hints:

const toon = `
users[2]{id,name,role,active}:
  1,Alice,admin,true
  2,Bob,user,true
`

const prompt = `
Given this user data:

\`\`\`toon
${toon}
\`\`\`

Extract the 'role' field for user with id=2.
`
// LLM sees field header and knows exactly where 'role' is positioned

Requesting TOON Output

When asking LLMs to generate TOON, provide header templates:

Specify Headers Explicitly

const prompt = `
Generate a list of 3 fictional products in TOON format.

Use this structure:

\`\`\`toon
products[3]{id,name,price,category}:
  <your data here>
\`\`\`
`

const response = await llm.complete(prompt)

Example-Based Generation

const example = encode({
  tasks: [
    { id: 1, title: 'Write docs', done: false },
    { id: 2, title: 'Run tests', done: true }
  ]
})

const prompt = `
Here's an example of TOON format:

\`\`\`toon
${example}
\`\`\`

Now generate 3 new tasks in the same format.
`

When requesting TOON output, show the exact header format you expect. LLMs will match the structure more reliably.

Validation and Parsing

Validating LLM Output

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

const llmResponse = `
users[2]{id,name}:
  1,Alice
  2,Bob
`

try {
  const data = decode(llmResponse, { strict: true })
  console.log('Valid TOON:', data)
} catch (error) {
  console.error('Invalid TOON output:', error.message)
  // Handle validation error
}

Extracting TOON from Text

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

const llmResponse = `
Here's the data you requested:

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

This dataset contains 2 users.
`

// Extract TOON code block
const match = llmResponse.match(/```toon\n([\s\S]*?)\n```/)
if (match) {
  const toon = match[1]
  const data = decode(toon)
  console.log(data)
}

Handling Malformed Output

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

async function parseLLMOutput(response: string, retries = 2) {
  const match = response.match(/```toon\n([\s\S]*?)\n```/)
  if (!match) {
    throw new Error('No TOON block found in response')
  }
  
  const toon = match[1]
  
  try {
    return decode(toon, { strict: true })
  } catch (error) {
    if (retries > 0) {
      console.log('Validation failed, requesting correction...')
      const fixPrompt = `
The previous TOON output was invalid:
\`\`\`toon
${toon}
\`\`\`

Error: ${error.message}

Please provide corrected TOON output.
      `
      const fixedResponse = await llm.complete(fixPrompt)
      return parseLLMOutput(fixedResponse, retries - 1)
    }
    throw error
  }
}

Real-World Integration Examples

RAG (Retrieval-Augmented Generation)

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

async function queryWithContext(question: string) {
  // Retrieve relevant documents
  const docs = await vectorDB.search(question, { limit: 10 })
  
  // Encode as TOON for token efficiency
  const context = encode({ documents: docs }, { delimiter: DELIMITERS.tab })
  
  const prompt = `
Context:

\`\`\`toon
${context}
\`\`\`

Question: ${question}

Answer based on the context above.
  `
  
  return await llm.complete(prompt)
}

Multi-Turn Conversations

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

class ConversationManager {
  private history: any[] = []
  
  async addMessage(role: string, content: any) {
    this.history.push({ role, content, timestamp: Date.now() })
  }
  
  async generatePrompt() {
    // Encode conversation history as TOON
    const historyTOON = encode(
      { messages: this.history },
      { delimiter: DELIMITERS.tab }
    )
    
    return `
Conversation history:

\`\`\`toon
${historyTOON}
\`\`\`

Continue the conversation naturally.
    `
  }
}

Structured Data Extraction

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

async function extractStructuredData(text: string) {
  const prompt = `
Extract entities from this text:

"${text}"

Provide output in TOON format:

\`\`\`toon
entities[N]{type,value,confidence}:
  <extracted entities>
\`\`\`
  `
  
  const response = await llm.complete(prompt)
  
  // Parse TOON output
  const match = response.match(/```toon\n([\s\S]*?)\n```/)
  if (match) {
    return decode(match[1])
  }
  
  throw new Error('Failed to extract structured data')
}

Batch Processing

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

async function batchAnalysis(items: any[]) {
  // Encode large dataset
  const toon = encode(
    { items },
    { delimiter: DELIMITERS.tab, keyFolding: 'safe' }
  )
  
  const prompt = `
Analyze this dataset:

\`\`\`toon
${toon}
\`\`\`

Provide summary statistics:
- Total count
- Average values
- Any anomalies
  `
  
  return await llm.complete(prompt)
}

Token Cost Optimization

Calculate Token Savings

import { encode } from '@toon-format/toon'
import { encode as encodeGPT } from 'gpt-tokenizer'

function compareTokens(data: any) {
  const json = JSON.stringify(data, null, 2)
  const toon = encode(data, { delimiter: '\t' })
  
  const jsonTokens = encodeGPT(json).length
  const toonTokens = encodeGPT(toon).length
  const saved = jsonTokens - toonTokens
  const percent = (saved / jsonTokens) * 100
  
  return {
    json: jsonTokens,
    toon: toonTokens,
    saved,
    percent: percent.toFixed(1)
  }
}

const data = { /* your data */ }
const stats = compareTokens(data)
console.log(`Token savings: ${stats.saved} (${stats.percent}%)`)

Cost Estimation

function estimateCost(data: any, pricePerMillion: number) {
  const stats = compareTokens(data)
  
  const jsonCost = (stats.json / 1_000_000) * pricePerMillion
  const toonCost = (stats.toon / 1_000_000) * pricePerMillion
  
  return {
    jsonCost: jsonCost.toFixed(4),
    toonCost: toonCost.toFixed(4),
    savings: (jsonCost - toonCost).toFixed(4)
  }
}

const pricing = estimateCost(data, 1.50)  // $1.50 per million tokens
console.log(`Cost with JSON: $${pricing.jsonCost}`)
console.log(`Cost with TOON: $${pricing.toonCost}`)
console.log(`Savings: $${pricing.savings}`)

Benchmark Results

From the README benchmarks:

Token Efficiency: TOON uses ~40% fewer tokens than JSON on mixed-structure datasets
Accuracy: 76.4% accuracy vs JSON’s 75.0% across 209 questions and 4 models
Efficiency Score: 27.7 accuracy%/1K tokens (best among all formats tested)

See full benchmark methodology and results in the README.

Best Practices

Use tab delimiters

Set delimiter: DELIMITERS.tab for ~5-10% additional token savings.

Wrap in code blocks

Always use ```toon code blocks when including TOON in prompts.

Show, don't describe

Provide examples instead of explaining TOON syntax.

Validate output

Use strict mode to catch malformed LLM responses early.

Monitor token usage

Track actual token counts and cost savings in production.

Token efficiency

Tab delimiters + key folding maximize token savings.

Structure validation

Length declarations [N] and field headers {fields} improve LLM accuracy.

Round-trip safety

Use expandPaths: 'safe' when decoding if encoded with keyFolding: 'safe'.

Format familiarity

CSV-like tables and YAML-like indentation are naturally understood.

When to Use TOON

✓ Uniform arrays

Large arrays of objects with consistent fields (tabular data).

✓ Token-sensitive apps

Applications where token costs matter (RAG, long contexts).

✓ Structured output

When requesting structured data from LLMs.

✗ Deeply nested

Highly nested structures may be better as compact JSON.

Next Steps

Encoding Guide

Learn all encoding options and transformations

CLI Usage

Use command-line tools for quick conversions

Streaming

Process large datasets efficiently

Get Started

Core Concepts

Usage Guides

Advanced

​Overview

​Why TOON for LLMs?

Token Efficiency

LLM-Friendly Structure

Human Readability

​Basic Integration

​Simple Data Encoding

​Showing Format Instead of Describing

​Optimal Formatting for LLMs

​Use Tab Delimiters

​Enable Key Folding

​Prompting Strategies

​Code Block Formatting

​Explicit Length Declarations

​Field Headers for Structure

​Requesting TOON Output

​Specify Headers Explicitly

​Example-Based Generation

​Validation and Parsing

​Validating LLM Output

​Extracting TOON from Text

​Handling Malformed Output

​Real-World Integration Examples

​RAG (Retrieval-Augmented Generation)

​Multi-Turn Conversations

​Structured Data Extraction

​Batch Processing

​Token Cost Optimization

​Calculate Token Savings

​Cost Estimation

​Benchmark Results

​Best Practices

Token efficiency

Structure validation

Round-trip safety

Format familiarity

​When to Use TOON

✓ Uniform arrays

✓ Token-sensitive apps

✓ Structured output

✗ Deeply nested

​Next Steps

Encoding Guide

CLI Usage

Streaming

Build docs developers (and LLMs) love

Overview

Why TOON for LLMs?

Basic Integration

Simple Data Encoding

Showing Format Instead of Describing

Optimal Formatting for LLMs

Use Tab Delimiters

Enable Key Folding

Prompting Strategies

Code Block Formatting

Explicit Length Declarations

Field Headers for Structure

Requesting TOON Output

Specify Headers Explicitly

Example-Based Generation

Validation and Parsing

Validating LLM Output

Extracting TOON from Text

Handling Malformed Output

Real-World Integration Examples

RAG (Retrieval-Augmented Generation)

Multi-Turn Conversations

Structured Data Extraction

Batch Processing

Token Cost Optimization

Calculate Token Savings

Cost Estimation

Benchmark Results

Best Practices

When to Use TOON

Next Steps