Okay, me and port just talked a bit on steam, you can do that in this case, but if you are using a method to get the second object (in this case the tool), you should use a seperate condition (as in my post), else it will throw a missing function error.
eg
isObject(%player = %client.player) is fine.
isObject(%tool = %client.player.tool[%x]) is fine.
isObject(%tool = %client.player.getTool(%x)) is not fine (assuming Player::getTool(%x) is defined), as if %client.player does not exist, then it will attempt to call 0.getTool(%x) (or similar), which will throw an error.
isObject(%player = %client.player) && isObject(%tool = %player.getTool(%x)) is the correct way to do it.
You could also remove the isObject calls if you know the function will return 0 or an empty string if the object does not exist. However, its much easier to read, more reliable, and closer to how its done in other languages, if you use isObject(%b = %a.b) && isObject(%c = %b.c)