I was often asked to provide feedback to people I worked with. Their manager would approach me, typically during probations, and ask: could you tell me what you think about this person? I was usually quite strict with my feedback which sometimes could be seen as harsh. My perspective was: I am giving feedback about this individual, but for their manager’s eyes only. A great tip I got to was: write it as if you were giving it directly to the person being evaluated. This is one of the single best advices I ever got.