:foreach a in=[/ip firewall address-list find list=blacklist] do={/ip firewall address-list set $a comment=[:resolve [/ip firewall address-list get $a address]]}} on-error={}
This is what I am talking about. But this is reverse lookup and not whois resolve.
Some guy posted something, but I did not read (yet) in full. http://forum.mikrotik.com/t/a-script-to-look-up-ip-to-rir-using-arin-whois/50820/1
Other sources?
json https://rdap.arin.net/registry/ip/8.0.0.0
put-an-address-by-hand style https://whois.arin.net/rest/net/NET-8-8-8-0-1/pft?s=8.8.8.8
No token based, but wait until you cross the https://www.arin.net/resources/registry/whois/tou/