I still don't completely know what intention is.
Intention is detailed in the Abhidharma as a mind that has an objective. Of course my knowledge of Abhidharma is weak so this is just a provisional definition.
In one buddhist post on the topic of harsh speech I read that (this was a post by a buddhist nun), if you accuse someone of something innapropriately --- and then upsets them then you have committid harsh speech.
Then we have the question for what is inappropriate, etc. However this appears to be a working Buddhist definition of harsh speech. I would add that you would seem to me to need to have had a goal of upsetting people but that may not be supported in the teachings.
I would add that Shakyamuni Buddha was detailed in several suttas about avoiding harsh speech by carefully examining one's speech and taught that it is better to not speak at all if there is a chance that the speech is not beneficial. This is the position of the Sravaka teachings. This position appears to not be significantly changed in the Mahayana teachings except when life is at stake.