• Racket provides JS-Expressions, which are a small subset of Scheme-forms, that can be converted to/from JSON. But that's Racket-only and uses hash-tables, which is not too nice in an API, given that our "Objects" will be small enough that performance won't force us to choose hash-tables over assoc lists.
  
• Given that for packhack we're currently only passing array of non-nested objects around, a list of assoc lists could already be good enough.
  
• It should be simple enough to map between a single assoc-list or a list of assoc-lists and the respective JSON-API of a Scheme implementation.
• And there is already SRFI-69 for mapping between assoc lists and hash-tables.
  

Since this is Scheme we could also use S-expressions instead of JSON as the "ground truth" format. Is there an established S-expression Schema specification (i.e. conventions for how to encode dictionaries and the like) -- ideally with a macro-based facility to unpack the S-exprs into hash-tables and the like.