[Virtual1ty]

If you want custom error messages when the command doesn't exist use this example:

Instead of returning 0 at OnplayerCommandText, use SendClientMessage and your own custom message.

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(!strcmp(cmdtext, "/test", true))
    {
        // Do something here
        return true;
    }
    return SendClientMessage(playerid, 0xFFFFFF, "CUSTOM: Unknown COMMAND");
}