Description

n8n-nodes-toon-converter

n8n community node for converting between JSON and TOON
Token-Oriented Object Notation — the format designed for LLMs

—

What is TOON?

TOON (Token-Oriented Object Notation) is a data serialization format created to reduce the number of tokens when passing structured data to LLMs. Same data model as JSON — objects, arrays, strings, numbers, booleans, null — but with a compact, line-based syntax.

Why does this matter?

Every token you send to an LLM costs money and counts against context limits. TOON solves this:

| Format | LLM Accuracy | Avg Tokens | vs JSON |
|——–|:————:|:———-:|:——-:|
| TOON | 76.4% | 2,759 | -40% |
| JSON (compact) | 73.7% | 3,104 | baseline |
| YAML | 74.5% | 3,749 | +21% |
| JSON (formatted) | 75.0% | 4,587 | +48% |

> Benchmark: 209 data retrieval questions across 4 LLM models. Source: toonformat.dev

Fewer tokens + higher accuracy = cheaper, faster, better AI workflows.

See the difference

{
  "hikes": [
    {"id": 1, "name": "Blue Lake Trail",
     "km": 7.5, "sunny": true},
    {"id": 2, "name": "Ridge Overlook",
     "km": 9.2, "sunny": false},
    {"id": 3, "name": "Wildflower Loop",
     "km": 5.1, "sunny": true}
  ]
}

hikes[3]{id,name,km,sunny}:
  1,Blue Lake Trail,7.5,true
  2,Ridge Overlook,9.2,false
  3,Wildflower Loop,5.1,true

—

Architecture

graph LR
    subgraph n8n Workflow
        A[Any Node] -->|JSON data| B["TOON Converter
Convert to TOON"]
        B -->|compact TOON string| C[AI / LLM Node]
        C -->|TOON response| D["TOON Converter
Convert to JSON"]
        D -->|structured JSON| E[Any Node]
    end
    style B fill:#E94560,stroke:#1A1A2E,color:#fff
    style D fill:#0F3460,stroke:#1A1A2E,color:#fff
    style C fill:#16C79A,stroke:#1A1A2E,color:#fff

How the node fits in your workflow

sequenceDiagram
    participant DB as Database / API
    participant TC1 as TOON Converter
    participant LLM as OpenAI / Claude
    participant TC2 as TOON Converter
    participant OUT as Output Node
    DB->>TC1: JSON data (verbose)
    Note over TC1: Convert to TOON
Auto-parse stringified JSON
Generate LLM instructions
    TC1->>LLM: TOON string (30-60% fewer tokens)
    LLM->>TC2: TOON response
    Note over TC2: Convert to JSON
Merge or put in field
    TC2->>OUT: Structured JSON

—

Node Operations

Convert to TOON

Transforms JSON data into compact TOON format before sending to an LLM.

| Parameter | Description |
|———–|————-|
| Source | Input Item / JSON Expression / JSON String |
| JSON Field | Optional: convert only a specific field |
| Output Field | Where to store the TOON string (default: toon) |

Convert to JSON

Parses TOON text back into structured JSON data.

| Parameter | Description |
|———–|————-|
| TOON Source | Input Field / TOON String |
| Output Mode | Merge Into Item / Put in Field |
| Output Field | Where to store the parsed data (default: data) |

Options (both operations)

| Option | Default | Description |
|——–|:——-:|————-|
| Keep Source Fields | true | Preserve original input fields in the output |
| Auto-Parse Stringified JSON | false | Detect and expand JSON.stringify()‘d fields before encoding — lets TOON compress the inner structure |
| Include LLM Format Instruction | false | Add a llmInstruction field that explains the TOON format to the LLM (format only, no data) |

—

Handling Stringified JSON

A common real-world pattern: your data has fields that contain JSON.stringify()‘d values:

{
  "user": "Ada",
  "preferences": "{"theme":"dark","lang":"es"}"
}

Without Auto-Parse (default)

The stringified JSON is treated as an opaque string — TOON wraps it in quotes:

user: Ada
preferences: "{"theme":"dark","lang":"es"}"

With Auto-Parse enabled

The node detects and expands stringified JSON fields before encoding:

user: Ada
preferences:
  theme: dark
  lang: es

This works recursively, handles double/triple stringified JSON, and is hardened against prototype pollution.

flowchart TD
    A[Input field value] --> B{Starts with
 curly or square bracket ?}
    B -->|Yes| C[Try JSON.parse]
    B -->|No| D[Keep as-is]
    C -->|Valid JSON| E{Is object/array?}
    C -->|Invalid| D
    E -->|Object| F[Recurse into each key]
    E -->|Array| G[Recurse into each element]
    F --> H{Key is proto /
constructor / prototype?}
    H -->|Yes| I[Skip key]
    H -->|No| J[Process value recursively]
    style I fill:#E94560,color:#fff
    style D fill:#0F3460,color:#fff

—

LLM Format Instruction

When Include LLM Format Instruction is enabled, the node adds a llmInstruction field to the output. This is a static, format-only explanation of TOON syntax — it does NOT include any data.

Use it in your AI node’s prompt before the TOON data:

{{ $json.llmInstruction }}
Here is the data:
{{ $json.toon }}
Now analyze this data and...

The instruction teaches the LLM how to read TOON: objects, tabular arrays, primitive arrays, and type inference rules — with inline syntax examples.

—

Security

This node is security-hardened with protections against common attack vectors:

graph TB
    subgraph "Security Layers"
        PP["Prototype Pollution
Protection"]
        RL["Recursion Depth
Limit (50)"]
        SV["Input Size
Validation (10MB)"]
        FK["Forbidden Key
Denylist"]
        SM["Safe Merge
(no Object.assign)"]
        SD["Static LLM Instruction
(no injection surface)"]
    end
    style PP fill:#E94560,color:#fff
    style RL fill:#E94560,color:#fff
    style SV fill:#E94560,color:#fff
    style FK fill:#E94560,color:#fff
    style SM fill:#E94560,color:#fff
    style SD fill:#E94560,color:#fff

| Threat | Mitigation |
|——–|————|
| Prototype pollution | safeMerge() replaces Object.assign() — skips proto, constructor, prototype. Objects built with Object.create(null). |
| Stack overflow (DoS) | Recursion capped at depth 50. |
| Memory bomb | Input size validated at 10MB before parsing. |
| Key injection | Output field names validated against forbidden key denylist. |
| Prompt injection | LLM instruction is fully static — no user data is embedded, eliminating the injection surface entirely. |
| Silent data mutation | No quoted-string unwrapping — only {...} and [...] patterns are parsed. |

Dependency audit

| Package | Risk | Notes |
|———|:—-:|——-|
| @toon-format/toon | Low | 0 runtime deps, 0 install scripts, SLSA provenance, 23K+ GitHub stars |

—

Test Suite

80 tests | 100% coverage | 0 vulnerabilities

 % Coverage report from v8
──────────────┬─────────┬──────────┬─────────┬─────────
File          │ % Stmts │ % Branch │ % Funcs │ % Lines
──────────────┼─────────┼──────────┼─────────┼─────────
All files     │     100 │      100 │     100 │     100
 converter.ts │     100 │      100 │     100 │     100
──────────────┴─────────┴──────────┴─────────┴─────────

Test breakdown

| Suite | Tests | What it covers |
|——-|:—–:|—————-|
| deepParseStringifiedJson | 17 | JSON stringified fields, edge cases, unicode, whitespace |
| convertToToon / convertToJson | 3 | Direct conversion, auto-parse toggle |
| TOON round-trip | 13 | All JSON types: objects, arrays, primitives, nesting |
| Stringified JSON handling | 6 | With/without auto-parse, tabular data, special chars |
| Full round-trip | 4 | Complex nested data, stringified preservation |
| Edge cases | 10 | Empty values, unicode, 100-row arrays, API patterns |
| LLM instructions | 5 | Format generation, sample embedding |
| Security: prototype pollution | 8 | proto, constructor, prototype in all paths |
| Security: recursion depth | 2 | 60-level nesting, deeply nested stringify |
| Security: input size | 4 | Size validation, oversized rejection |
| Security: prompt injection | 3 | Backtick sanitization, normal content preservation |
| Security: string mutation | 3 | No silent "42" -> 42 coercion |
| Security: global check | 1 | Object.prototype cleanliness after all tests |

CI Pipeline

Tests run on every push and PR via GitHub Actions across Node.js 20 and 22:

.github/workflows/ci.yml
jobs:
  test:       # Runs tests on Node 20, 22
  coverage:   # Generates coverage report
  typecheck:  # Strict TypeScript validation

—

Installation

Via n8n UI (recommended)

1. Go to Settings > Community Nodes
2. Click Install
3. Enter n8n-nodes-toon-converter
4. Restart n8n

Via CLI

cd ~/.n8n
npm install n8n-nodes-toon-converter
Restart n8n

Docker

FROM n8nio/n8n:latest
RUN cd /usr/local/lib/node_modules/n8n && 
    npm install n8n-nodes-toon-converter

—

Workflow Examples

1. Compress data before LLM analysis

[PostgreSQL] → [TOON Converter: Convert to TOON] → [OpenAI Chat]

Save 30-60% tokens on every LLM call by converting query results to TOON first.

2. Instruct LLM to respond in TOON

Enable Include LLM Instructions and pass llmOutputInstruction in the system prompt. The LLM responds in TOON, saving output tokens too.

[TOON Converter] → [OpenAI: uses llmOutputInstruction] → [TOON Converter: Convert to JSON]

3. Auto-parse API responses with stringified JSON

APIs often return fields with JSON.stringify()‘d values. Enable Auto-Parse Stringified JSON to let TOON compress the inner structure.

[HTTP Request] → [TOON Converter: auto-parse + convert] → [AI Agent]

—

TOON Syntax Quick Reference

| Structure | Syntax |
|———–|——–|
| Object | key: value (indented for nesting) |
| Tabular array | key[N]{f1,f2}: + CSV rows |
| Primitive array | key[N]: a,b,c |
| Mixed array | key[N]: + - item per line |
| String quoting | Only when value contains : , [ ] { } or looks like a number/boolean |
| Empty array | key[0]: |

Full spec: github.com/toon-format/spec

—

Project Structure

n8n-nodes-toon-converter/
  nodes/ToonConverter/
    ToonConverter.node.ts     # n8n node definition
    ToonConverter.node.json   # Codex metadata for n8n search
    converter.ts              # Pure conversion logic (100% tested)
  icons/
    toon.svg                  # Node icon
  tests/
    ToonConverter.test.ts     # 80 tests (functional + security)
  docs/                       # Extended documentation
  .github/workflows/
    ci.yml                    # Test + typecheck + coverage
    publish.yml               # npm publish with SLSA provenance

—

Documentation

| Document | Description |
|———-|————-|
| What is TOON? | Format overview, benchmarks, when to use it |
| Usage Guide | Detailed node parameter reference |
| Examples | Practical workflow patterns |
| TOON Syntax Reference | Complete syntax cheatsheet |
| Installation Guide | All installation methods |

—

Links

• TOON Official Site — Format specification and benchmarks
• TOON TypeScript SDK — The library this node uses
• n8n Community Nodes — How community nodes work
• TOON Spec — Formal specification

—

Contributing

git clone https://github.com/arodriguezp2003/n8n-nodes-toon-converter.git
cd n8n-nodes-toon-converter
npm install --ignore-scripts
npm run build    # Compile TypeScript
npm test         # Run 80 tests

—

Author

Alejandro Rodriguez — LinkedIn

—

License

MIT