...

• compile-time checks for plugin metadata, with enums for some annotations
• inheritance support
• annotations are supported in most IDEs, providing code-completion and syntactic checks

see plexus-component-annotations for an example of such a work done on Plexus.

Existing implementations

Multiple implementations of such annotations exist:

• JFrog's Maven Anno Mojo: see the wiki or annotations source,
  the idea is having as much annotations as actual javadoc annotations, each with only 1 attribute
• Maven MNG-2521, with its proposal from 2007 providing a source branch and its annotations,
  the idea is having only 4 annotations each with multiple attributes: Goal + Execute and Parameter + Component

Proposal

Annotations:

• 4 annotations: Mojo, MojoExecute, MojoParameter and MojoComponent
• java package: org.apache.maven.tools.plugin.annotations (consistent with maven-plugin-tools-api
• component: maven-plugin-tools-annotations in plugin-tools

Extractor: addition to maven-plugin-tools-javaWIP