JSON does not have any numberic types other than "number". Nor does it have dates (values must be stringified).
The GetType(<property-name>) method returns a NUMBER value but that could refer to INT, INT64 or DECIMAL values. The ABL should provide more guidance on what the values could be. This may be via IsInteger()/IsINt64()/IsDecimal() methods or a GetNumericType() method that could return a flagged Enum. Some values - like 12 - could be INT, INT64 and DEC.
This functionality would help devs write less try-check code and make working with JSON easier
Good Idea !
Speaking of help with numbers, Progress should support parsing (not generating) numbers using exponential notation, since that is valid JSON.