ctcp <target> clientinfo <ctcp command>
This CTCP request roughly acts as a “help” command. If you do not provide any arguments, the other person's client will give you a list of which CTCP requests it supports. If you give it an argument, the other person's client will give you information about its implementation of that CTCP request.
Some CTCP commands are intended for internal use only. Avoid direct use of ctcp dcc, ctcp errmsg, and ctcp sed.
Many clients may not fully support ctcp clientinfo.
To find out which CTCP requests john's client supports:
/ctcp john clientinfo
To get more information on CTCP VERSION from joebob:
/ctcp joebob clientinfo version
# $EPIC: ctcp_clientinfo.txt,v 1.3 2006/07/24 19:50:14 sthalik Exp $