gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep version
RSA is recommended:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep -A2 '^:public key packet:$' | grep algo
RSA with 4096 bit is recommended:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep -A2 'public key' | grep 'pkey\[0\]:'
Self Signatures should not be done with MD5:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep -A2 'signature' | grep 'digest algo 1,'
Self Signatures should not be done with SHA1:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep -A2 'signature' | grep 'digest algo 2,'
Key should use SHA2 as prefered digest:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep 'pref-hash-algos'
Key should have expiration date:
gpg --export-options export-minimal --export KEY_ID | gpg --list-packets | grep 'key expires after'