[nomel]

> with an off-the-shelf parser as stdin

These only exist for well known tools. And, these usually explode if you're not careful about the characters in your filename.

[fiddlerwoaroof]

That’s not what I’m saying: your program expects to receive standard input in json format. And uses your favorite JSON parsing library to handle stdin. Generate stdout as JSON with the same library. Then, use jq to generate the standard input and output.