[techhazard]

Not OP, but I can highly recommend just using the programming language you already use to make key-value map to and then converting that to JSON. That way you only have 1 syntax to worry about. In my case that’s Python (using dictionaries and json.dumps)

You could also try for a templating framework (like jinja2) but then you have 3 syntaxes colliding: the programming language you call the templating engine with (e.g. Python for jinja2) the templating language itself (e.g. jinja2) and then JSON as well.

[spion]

This works for some languages but not others (some typed languages are particularly ill-suited to the problem of writing CLI tools to dump heterogenous dictionaries and/or objects with many optional fields)