-.B gen-subkey KEYID
-Generate an authentication subkey. For the primary key with the
-specified key ID, generate a subkey with "authentication" capability
-that can be used for monkeysphere transactions. An expiration length
-can be specified with the `-e' or `--expire' option (prompt
-otherwise). `g' may be used in place of `gen-subkey'.
+.B gen-subkey [KEYID]
+Generate an authentication subkey for a private key in your GnuPG
+keyring. For the primary key with the specified key ID, generate a
+subkey with "authentication" capability that can be used for
+monkeysphere transactions. An expiration length can be specified with
+the `-e' or `--expire' option (prompt otherwise). If no key ID is
+specified, but only one key exists in the secret keyring, that key
+will be used. `g' may be used in place of `gen-subkey'.