[UFF]

pawn Код:

CMD:setskin(playerid, params[]) 
{ 
    new targetid, skinid, str[90], name[MAX_PLAYER_NAME]; 
    if(sscanf(params, "ii", targetid, skinid))  
    return SendClientMessage(playerid, -1, "[USAGE]: /setskin [playerid] [skinid]"); 
    SetPlayerSkin(targetid, skinid); 
    GetPlayerName(targetid, name, sizeof(name));
    format(str, sizeof(str), "You have set %s's skin id to %i.",name, skinid);
    SendClientMessage(playerid, -1, str);
    return 1; 
}

SendClientMessage has only 3 paramaters, use format for those.