toon-fu

https://github.com/hoblin/toon-fu

Encodes Ruby hashes, arrays, dates and your own objects into TOON, the token-efficient format for LLM prompts: tables for uniform arrays, quotes only where needed. The only Ruby TOON gem that passes all of the current spec's encode fixtures; its version tracks the spec it implements, and anything it cannot represent raises an error so your data arrives complete.