As far as I know, F5 does not have documentation for every log message. On my 11.5.x box, there are >5000 messages:
wc -l /var/run/bigip_error_maps.dat
5240 /var/run/bigip_error_maps.dat
sol6420: The /var/run/bigip_error_maps.dat file maps the alertd process input from the syslog-ng utility to an alert name
They do have documentation in the manual for SNMP traps which are most likely the most important log messages. That is a pretty good document:
Monitoring BIG-IP System Traffic with SNMP
https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-external-monitoring-implementations-11-4-0/8.html?sr=41320821
Hope this helps.