[dansimau]

> How do you expect jo to know where the 1 came from to change its interpretation?

It was merely an observation. Of course, one can simply negate the value before passing it to jo.

jo looked as though it was for use in the shell though, so I was curious as to the design decision here.

[kbd]

> It was merely an observation... jo looked as though it was for use in the shell though, so I was curious as to the design decision here.

I think it makes sense how it is, since if I typed "success@1" I wouldn't expect that to output "{success: false}" but I definitely appreciate your point about a case like "success@$?".

> Of course, one can simply negate the value before passing it to jo.

What's the shortest way to do that? This?

    echo success@$(test $? -ne 0; echo $?)

[kbd]

Shortest way:

    $ false; echo success@$((! $?))
    success@0

[jpmens]

I intended True to be, well, TRUE (1). TBH I didn't consider a shell's success (0) as true, though I do see your use-case.