I have no idea what people are complaining about in this thread. I find projects like this genius. I love making programming languages and I hate hate hate writing parsers, yet I enjoy experimenting with different syntax. Stuff like this is very convenient because you can just import your code as document, use path language to extract data, and schema language to apply basic checks. Not only is this thing standardized[1], it's implemented in your favorite language (Rust, Python, Java whatever).
[1] EDIT: to be clear here, I meant to say it has a specification. I'm guessing your handbaked language won't have.