TOON to JSON

Decode TOON back to JSON

TOON — Token-Oriented Object Notation — is a compact text format for the JSON data model built to save tokens when you pass structured data to large language models. Nested objects use YAML-like indentation, and arrays of objects with identical keys become tables: the header users[2]{id,name}: declares the length and field names once, and each following line holds one row of comma-separated values. That removes the repeated braces, quotes and keys that make JSON expensive, often cutting token counts by 30–60% for tabular data.

The catch is that the rest of your stack still speaks JSON. When a model answers in TOON, or when you inherit a prompt fixture written in TOON, this TOON to JSON converter turns it back into standard JSON you can feed to JSON.parse, an API, a test, or a database. It uses the official @toon-format/toon decoder, so quoting rules, escapes, alternative delimiters (tab and pipe), list items with - and nested tables are all handled exactly as the specification defines.

Validate LLM output with strict mode

Because TOON declares [N] lengths, it can detect a truncated or hallucinated answer that JSON would silently accept. With Strict mode on, the decoder fails with a clear message when an array has fewer or more items than declared, a table row has the wrong number of fields, or indentation is inconsistent. That makes it a useful guardrail when you ask a model to produce TOON: decode, and reject the response if validation fails. If you just need to salvage what is there, switch strict mode off and the converter keeps whatever rows parse.

Tips for working with TOON

TOON shines for uniform arrays of objects — log lines, product lists, search results, analytics rows. Deeply nested or irregular data compresses less, and plain JSON may even be smaller. Numbers, true, false and null are typed automatically; quote a value such as "007" to keep it a string. Use the Minified indent option for the smallest JSON, or two spaces for review. Need a different target? The same decoder powers the TOON to YAML, TOON to XML and TOON to CSV converters, and you can tidy the result further with the JSON formatter. Everything runs locally, so prompts and data never leave your device.