The minimum descent rate required during the various segments of flight is the one that gives you a nice, stable descent and prevents you from busting any limiting altitude/s in the procedure. "ICAO standards" don't talk about that because they figure that most pilots can read a chart and work out the minimum descent required in each segment. Pans Ops - a "document", rather than a "standard" - works on a maximum descent rate to, firstly, ensure that obstacle clearance criteria won't be breached and, secondly, for aircraft configuration purposes and avoiding excessive rate of descent.