The JSON format is extremely simple, and there are good, fast parsers available for a number of programming languages. We first started developing Chemical JSON as a simple format for the Open Chemistry project, The development was initially specified in an ad-hoc fashion on the wiki. The versions currently in use, and documented there were developed to facilitate addition of property arrays mapped to atoms and/or bonds, they map quite directly to Avogadro 2's in-memory representations, and are also stored efficiently in BSON (the binary JSON representation used by MongoDB).
In parallel to this there has been development of JSON representations for computational chemistry output from the NWChem code, continuing on from early work to extend CML. We have started to explore the extension of Chemical JSON for a number of applications, and methods for improving it by bringing in JSON-LD concepts.
This repository is being set up to facilitate collaboration on the use of JSON represntations for chemistry, and to document those representations more formally than has been done in the past.