how to get key value in trigger description?

[lalazhu]

I wanna send an alert email with cpu info. I try to insert a key expresson in trigger description. But it doesnot work, like this: system.hw.cpu[,curfreq].
And also try the following expresson in email template like the below:
{Template OS Linux:system.hw.cpu[,curfreq]}

{{HOST.NAME}:system.cpu.num}
{system.cpu.num}

{system.hw.cpu[,curfreq]}

{{HOST.HOST}:system.hw.cpu[,curfreq].last()}

It is still does not work.

How to get cpus when trigger was trigged ?