The existing tools for address checking in VyOS are often too broad for convenient checking. Split IPv4 and IPv6 VRRP (T616) makes this especially apparent, since we need to check for IPv4 OR IPv4 with prefix length, or IPv6 OR IPv6 with prefix length, but we don't have a ready to use tool.
ipaddrcheck was intended to solve exact this issue back in Vyatta, but somehow it never made it to the image. Time to fix it.