What is the format that linters are expected to produce

[Philip White]

I'm trying to provide syntax highlight for a small language I have. I
would like to also provide a formatter and a linter. The formatter I
have successfully created, but I can't find any type of documentation
for what a linter is expected to do. My guess was that it would just
need to spit out some lines like

    filename:10:10 some error

But setting the linter to

    linter echo filename:10:10

still report 0 linter items.

Is there documentation somewhere for the expected behavior of a linter.
If not, can someone explain it to me?

Thanks!