ASM Custom attack signature rule

I want to block some specific keywords in my post request like i.e Block through an attack signature. What would be the script for Rule section in attack signature creation page.

 

I have created below script can some one validate this please and correct me where I am wrong.

 

content:"Block";nocase; to search the keyword block

 

uricontent:"POST"; to find the method in request line it should be POST