It would be nice if the complete MDC map with all it's entries got logged if you use %X in your log pattern without specifying a key (e.g. %X{key1}).

Similar to logback: https://logback.qos.ch/manual/layouts.html#mdc
where it would be output as:
key1=val1, key2=val2

Or log4j: https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/EnhancedPatternLayout.html
where it would be output as: 
{{key1,val1},{key2,val2}}