Try this
"request snmp spoof-trap jnxEventTrap variable-bindings \"jnxEventTrapDescr = Daily-Freshness-Check\""
Here's a few working examples for event-option to execute pfe/re shell commands. Should be supported:
set event-options policy test then execute-commands commands "start shell sh command \"/sbin/sh /var/home/labroot/cmd.sh\" | no-more"
set event-options policy high-cpu then execute-commands commands "request pfe execute target tnp tnp-name fpc1.pic0 command \"show usp jexec event\""
set event-options policy log-on-snmp-trap-link-down then execute-commands commands "request pfe execute command 'show syslog messages ' target fpc0 | no-more"