SNMP, MIB for traps

Hello,

I`m developing a device which will use SNMP traps
to tell that there is some problem.
I set up snmptrapd server.
I send traps from a device with use of snmptrap application.
I have got my enterprise ID.
I could send some traps.

The problem is that I don`t understand function of MIB in traps.
What does MIB (snmp v1) should look like in my case ?
I have got my enterprise ID. I would like to send traps
with numbers which tell what kind of error appeared on my device.
E.g. number "1" means that the temperature of a device is too low,
"2" means that a laser system has detected an object,
"3" means that somebody forgot to close a door.

Thanks in advance,
Pavel.