I Don't know ICAO, but in the US ATC expects optimal normal climb and descent performance in accordance with normal operating procedures for that aircraft. For the last 1,000' approaching your target altitude your desecnt rate is to be slowed to 1,000 fpm (+/- 500fpm).
If you are unable to climb at 500 fpm you are required to advise ATC. This of course applies to reciprocating engine (especially non-turbocharged) aircraft that lose engine power with altitude- not turbine aircraft.
Are you asking for the purposes of flying flight simulator?
Would you like to know how to calculate desent rates for various airspeeds and desent profiles as a pilot or are you only curious about regulatory requirements?