Easy to reach, easy to overload
Kamakura is useful from Tokyo because it gives temples, coast and calmer streets. It fails when you try to do everything.
Half day or full day
A half day works for contrast and lighter pacing. A full day is better if Kamakura is a main stop.
Temples or sea
Prioritize temples if Kyoto is short or absent. Prioritize coast if Tokyo needs air and a softer day.
Practical choice
Choose two or three anchors, not every famous stop. Lunch, shoes and weather matter more than the map suggests.
Compare with other day trips
Kamakura is usually easier than Nikko and lighter than Hakone, but less dramatic than both.