36f71d6e_Tools_Javadoc_Taglets_3_4_API___Notes
[Descriptor Element] required [Annotation] @required [Required?] No [Notes] 
Whether this parameter is required for the Mojo to function. This is used to validate the configuration for a Mojo before it is injected, and before the Mojo is executed from some half-state. NOTE: Specification of this annotation flags the parameter as required; there is no true/false value.
org.apache.maven.tools.plugin.javadoc (Maven Plugin Tools Javadoc Taglets 3.4 API)