There will always be one tag. It contains one line for each breakpoint. First arg is the segment it is defined in (so if you turn on and off segments you can switch breakpoints on an off too). Second argument is the address it is defined at (You will not need it in eg. .break "nmi", but it is always there). Third argument is whatever the user writes in the .break
argument and might be empty. So .break "nmi" and .break "cia" will give nmi and cia.
From C64Debugger manual: