UCI protocol: giving up!

[hgm]

There is actually a de-facto standard for score POV

Which is...?
I always report the scores used internally, which are side-to-move POV. But I'd be happy to convert them if needed.

Side-to-move POV is indeed what the overwhelming majority of engines uses when thinking. During ponder it is less clear, though: some engines (in particular those that ponder the position, rather than a specific move, report with opposite sign during ponder). Of course ponder scores are still not used for anything.