To chase this - converting to json or another standardized format in every single case where someone is tempted to write their own custom parser. Never write custom parsers kids, they're an absolutely horrible time-suck and you'll be fixing them quite literally forever as you discover new and interesting ways for your input data to break them.
Edit: it doesn't have to be json, I really don't care what format you use, just pick an existing data format that uses a robust, thoroughly tested, parser.
To add to that. Configuration file formats...just pick a standard one, do not write your own.
And while we are at it, if there is even a remote chance that you have a "we will do everything declaratively" idea, just use an existing programming language for your file format instead of painfully growing some home-grown add-ons to your declarative format over the next decade or two because you were wrong about only needing a declarative format.