The same with reading lte cell-monitor feature…
Only way I know is via file… http://forum.mikrotik.com/t/send-script-output-to-a-file/116250/1
execute "/tool snmp-walk community=public version=2c address=127.0.0.1 oid=1.3.6.1.2.1.1" file=out.txt
file edit out.txt contents
global out2 [file get out.txt contents]
put [typeof $out2]
str