vyos@vyos# sudo nft describe icmp type
payload expression, datatype icmp_type (ICMP type) (basetype integer), 8 bits

pre-defined symbolic constants (in decimal):
	echo-reply                    	                   0
	destination-unreachable       	                   3
	source-quench                 	                   4
	redirect                      	                   5
	echo-request                  	                   8
	router-advertisement          	                   9
	router-solicitation           	                  10
	time-exceeded                 	                  11
	parameter-problem             	                  12
	timestamp-request             	                  13
	timestamp-reply               	                  14
	info-request                  	                  15
	info-reply                    	                  16
	address-mask-request          	                  17
	address-mask-reply            	                  18

vyos@vyos# set firewall name FOO rule 10 icmp type-name 
Possible completions:
   any          Any ICMP type/code
   echo-reply   ICMP type/code name
   pong         ICMP type/code name
   destination-unreachable
                ICMP type/code name
   network-unreachable
                ICMP type/code name
   host-unreachable
                ICMP type/code name
   protocol-unreachable
                ICMP type/code name
   port-unreachable
                ICMP type/code name
   fragmentation-needed
                ICMP type/code name
   source-route-failed
                ICMP type/code name
   network-unknown
                ICMP type/code name
   host-unknown ICMP type/code name
   network-prohibited
                ICMP type/code name
   host-prohibited
                ICMP type/code name
   TOS-network-unreachable
                ICMP type/code name
   TOS-host-unreachable
                ICMP type/code name
   communication-prohibited
                ICMP type/code name
   host-precedence-violation
                ICMP type/code name
   precedence-cutoff
                ICMP type/code name
   source-quench
                ICMP type/code name
   redirect     ICMP type/code name
   network-redirect
                ICMP type/code name
   host-redirect
                ICMP type/code name
   TOS-network-redirect
                ICMP type/code name
   TOS host-redirect
                ICMP type/code name
   echo-request ICMP type/code name
   ping         ICMP type/code name
   router-advertisement
                ICMP type/code name
   router-solicitation
                ICMP type/code name
   time-exceeded
                ICMP type/code name
   ttl-exceeded ICMP type/code name
   ttl-zero-during-transit
                ICMP type/code name
   ttl-zero-during-reassembly
                ICMP type/code name
   parameter-problem
                ICMP type/code name
   ip-header-bad
                ICMP type/code name
   required-option-missing
                ICMP type/code name
   timestamp-request
                ICMP type/code name
   timestamp-reply
                ICMP type/code name
   address-mask-request
                ICMP type/code name
   address-mask-reply
                ICMP type/code name
   TOS

vyos@vyos# set firewall name FOO rule 10 action accept
[edit]
vyos@vyos# set firewall name FOO rule 10 protocol icmp
[edit]
vyos@vyos# set firewall name FOO rule 10 icmp type-name echo-request
[edit]
vyos@vyos# commit
[edit]
vyos@vyos# set firewall name FOO rule 30 action accept
[edit]
vyos@vyos# set firewall name FOO rule 30 protocol icmp
[edit]
vyos@vyos# set firewall name FOO rule 30 icmp type-name fragmentation-needed 
[edit]
vyos@vyos# commit
[ firewall ]
Failed to apply firewall

[[firewall]] failed
Commit failed

table ip filter {
    chain FOO {
        meta l4proto icmp icmp type echo-request counter return comment "FOO-10"
        meta l4proto icmp icmp type fragmentation-needed counter return comment "FOO-30"
        return