It depends… some people like to include tons of details like tempo, rest intervals and the likes.
At the minimum it should have enough information that someone who picks up your “program” can do it and it would be pretty much exactly what you had in mind when you wrote it,
I think that it needs to include…
Workout structure (how are the exercises organized… order, combinations, etc.)
Loading parameters (sets/reps/load)
Information about how the reps are done
At least a broad idea of the rest intervals
Some coaches include more details, but I feel that this is a minimum