Lets talk about FeatureDescriptor, the superclass for all other descriptors. It enables to add extra metadata to describe the beans. The builder tool could use such metadata to provide enhanced functionality. You can use the getValue(String) method to retrieve metadata. For example: BeanInfo info = Introspector.getBeanInfo(JLabel.class); Object value = info.getBeanDescriptor().getValue("isContainer"); boolean isContainer = (value instanceof Boolean) && (Boolean)value; The following attributes are supported in JDK. Other beans creators can use their own attributes and support them in own builder tools. See JavaBean BeanInfo Attributes and JavaBeans in JFormDesigner articles for details and examples on how to use attributes.
Read Sergey's entire post: http://weblogs.java.net/blog/malenkov/archive/2007/10/javabeans_featu_1.html