The nested header started as an RFC from Noah Nyholm – with grammar, benchmarks, and test cases. Thanks!
Also in v4: keyed tabular form, comment lines, key folding removed.
All the changes: toonformat.dev/guide/whats-...
toonformat.dev
TOON
Token-Oriented Object Notation (TOON) – compact, human-readable serialization of JSON data for LLM prompts