Methods MethodTypeDesc:changeReturnType, ofDescriptor have the ​assertion: Throws: NullPointerException - if any argument is null. It should be reworded because methods have only one parameter.

Method j.l.c.MethodHandleDesc:asType - missing assertion:
Throws NullPointerException - if the argument is null

Cosmetic issue:
All assertions of class MethodTypeDesc that define ranges use the syntax
 {[ start, end]} except the method dropParameterTypes that uses [0, parameterCount] for the end parameter i.e. there are missing curly brackets