The $METHODINFO switch directive is only effective when runtime type information (RTTI) has been turned on with the {$TYPEINFO ON} switch. In the {$TYPEINFO ON} state, the $METHODINFO directive controls the generation of more detailed method descriptors in the RTTI for methods in an interface. Though {$TYPEINFO ON} will cause some RTTI to be generated for published methods, the level of information is limited. The $METHODINFO directive generates much more detailed (and much larger) RTTI for methods, which describes how the parameters of the method should be passed on the stack and/or in registers. 

There is seldom, if ever, any need for an application to directly use the $METHODINFO compiler switch. The method information adds considerable size to the executable file, and is not recommended for general use.