What is TOML format?

TOML (Tom's Obvious, Minimal Language) is a configuration file format designed to be easy to read and write due to its obvious semantics. Created by Tom Preston-Werner (GitHub co-founder), TOML maps unambiguously to a hash table and is commonly used for configuration files in Rust projects (Cargo.toml), Python tools, and many other applications. It uses a clear, minimal syntax with sections denoted by square brackets and key-value pairs similar to INI files but with richer data types including arrays, nested tables, dates, and proper type handling.

Tool Description

This converter transforms data between TOML and TOON formats bidirectionally. Convert TOML configuration files to token-efficient TOON format for LLM processing, or transform TOON data back to standard TOML. The tool uses the official @toon-format/toon and smol-toml libraries to ensure accurate conversion. This is particularly useful when working with LLMs on configuration management tasks, infrastructure-as-code scenarios, or any situation where you need to process TOML data efficiently within token constraints.

Examples

TOML Input:

[database]
server = "192.168.1.1"
ports = [8000, 8001, 8002]
enabled = true

[[servers]]
name = "alpha"
ip = "10.0.0.1"
role = "frontend"

[[servers]]
name = "beta"
ip = "10.0.0.2"
role = "backend"

TOON Output:

database:
  server: 192.168.1.1
  ports: [8000,8001,8002]
  enabled: true
servers[2]{name,ip,role}:
  alpha,10.0.0.1,frontend
  beta,10.0.0.2,backend

Configuration File Example:

TOML configuration with nested structures:

[app]
name = "MyApp"
version = "1.0.0"

[app.settings]
debug = false
timeout = 30

[[app.features]]
id = 1
name = "feature-a"
enabled = true

[[app.features]]
id = 2
name = "feature-b"
enabled = false

Becomes compact TOON:

app:
  name: MyApp
  version: 1.0.0
  settings:
    debug: false
    timeout: 30
  features[2]{id,name,enabled}:
    1,feature-a,true
    2,feature-b,false

Features

  • Bidirectional conversion between TOML and TOON formats with full fidelity
  • Token reduction for LLM processing (30-50% fewer tokens for structured configs)
  • Preserves TOML semantics including tables, arrays of tables, and nested structures
  • Type-safe conversion maintaining integers, floats, booleans, strings, and arrays
  • Real-time conversion with instant results as you type

Use Cases

  1. Configuration Analysis with LLMs - Convert TOML config files to TOON format before sending to LLMs for analysis, suggestions, or documentation generation with reduced token costs
  2. Infrastructure-as-Code Processing - Transform Terraform, Cargo, or other TOML-based configurations for efficient LLM-based infrastructure reviews and modifications
  3. CI/CD Configuration Management - Process build configuration files through LLMs for optimization or migration while minimizing API costs
  4. Settings Migration - Convert application settings between formats when integrating with LLM-powered configuration management tools
  5. Documentation Generation - Prepare TOML configurations for LLM-based documentation writers using token-efficient encoding

Conversion Details

The converter handles TOML-specific features appropriately:

  • Tables ([section]) convert to nested objects in TOON with indentation
  • Arrays of tables ([[array]]) convert to TOON's tabular format when uniform
  • Inline tables ({key = value}) preserve structure through proper nesting
  • Data types (strings, integers, floats, booleans, dates) maintain type safety
  • Arrays convert to TOON array notation with proper formatting
  • Dotted keys (a.b.c = value) expand to nested structure

Token Efficiency

Converting TOML to TOON before LLM processing provides significant savings:

Example Token Comparison (50 server configurations):

  • TOML (formatted): ≈ 12,500 tokens
  • TOON: ≈ 7,200 tokens (42% reduction)
  • TOON benefit: More data within context window, lower API costs

The savings are most pronounced with:

  • Repeated table structures (like [[servers]], [[databases]])
  • Arrays of similar configuration objects
  • Large configuration files with uniform sections
  • Multi-environment configs with similar structure

Format Compatibility

TOML Features Supported:

  • Basic key-value pairs
  • Tables and nested tables
  • Arrays of tables
  • Inline tables and arrays
  • All TOML data types (string, integer, float, boolean, datetime, array, table)
  • Comments (preserved in structure, though not in TOON representation)

Round-Trip Fidelity: TOML → TOON → TOML conversion maintains data integrity, though formatting and comments may be normalized. The semantic meaning and all values are preserved.

When to Use This Converter

Use TOML → TOON when:

  • Sending configuration files to LLMs for analysis or modification
  • Processing large TOML configs within token limits
  • Batch processing multiple config files through LLM APIs
  • Generating documentation from TOML configurations

Use TOON → TOML when:

  • Converting LLM-generated configurations back to standard format
  • Integrating LLM output into TOML-based toolchains
  • Creating human-editable config files from compact data
  • Preparing output for TOML-native applications