After Sakai 10 release, I've detected some artifacts missing in sonatype repository. So, if you want to compile a contrib tool, you won't be able to do it without previously download and compile Sakai source.
1.- Utils artifacts:
2.- Parent poms (between released artifact and master):
These are only some examples of missing pom files, but actually every api artifact should have its parent pom published on sonatype, calendar, announcement, ...