Token-Oriented Object Notation (TOON)
Token-Oriented Object Notation is a compact, human-readable format designed for passing structured data to Large Language Models with significantly reduced token usage.
TOON excels at uniform complex objects – multiple fields per row, same structure across items. It borrows YAML's indentation-based structure for nested objects and CSV's tabular format for uniform data rows, then optimizes both for token efficiency in LLM contexts.
Why TOON?
AI is becoming cheaper and more accessible, but larger context windows allow for larger data inputs as well. LLM tokens still cost money – and standard JSON is verbose and token-expensive:
{ "users" : [ { "id" : 1 , "name" : " Alice " , "role" : " admin " }, { "id" : 2 , "name" : " Bob " , "role" : " user " } ] }
TOON conveys the same information with fewer tokens:
users[2]{id,name,role}: 1,Alice,admin 2,Bob,user
Another reason
Format Comparison
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