What to include in a letter of support for an academic assessment?
I would suggest by starting with a general statement about your colleague as an academic (quality of work, productivity etc. relative to others, in general, in the specific sub-discipline) following that you could exemplify this with the points you mention. Tiyr second paragraph could almost be copied into such a letter but with some more detail. A second item may be to set the last year performance in perspective of the longer term. This seems not to be asked for but I think it is a valuable step to set the year's performance in perspective both relative to what has been achieved earlier and relative to what can be expected visavi the person's job siuation (teaching load, admin load etc.. For tenure, I suppose personal traits and activities within the department are not of interest since they would be known internally. Other wise such points should be included.