The idea is that descriptions like: local:tools:app-crypt/gnupg: Install extra tools. tell us nothing and we have to either install to see if that's something useful, or look through websites, etc. Really no point in describing the flag then.
Handy filing URL: https://bugs.gentoo.org/enter_bug.cgi?product=Gentoo%20Linux&component=Current+packages&short_desc=%s:+useless+USE=tools&comment=%s%0a%0aIt+would+be+really+nice+if+this+could+be+extended+to+state+what+tools+are+installed,+i.e.+letting+the+user+choose+without+having+to+conduct+additional+research.&blocked=600712