Inventory Slot Detection

In Sethbling's snapshot 14w07b video, he uses a command block to give him jump boost while he is wearing his Boots of Leaping.

I am trying to imitate this for a multiplayer map I am making. Wearing golden boots called "Stealth Boots" is supposed to give that player invisibility. I am using this command:

/effect @a[Inventory:[{Slot:100b,tag:{display:{Name:"Stealth Boots"}}}]] 14 30000 200

I do know that in the video he is using a /testfor command, but since I'm making a multiplayer map in order to use this technique I'd have to define a scoreboard variable for each player - and even then, the players would be finite. Thus, I want to be able to use the command DIRECTLY.

When I use that command, it either says "That player cannot be found" or "The entity UUID provided is in an invalid format" - the former of which I'm familiar with; the later I've barely ever seen before.

So, my method doesn't seem to work - how do I fix it?

As of 14w10c, this is possible using scoreboard values.

First, you need to set up a dummy scoreboard variable. I used "sneaky" as my variable, but you can really use whatever you want (as long as you change the commands as appropriate). To set this up, you just need to use the command /scoreboard objectives add sneaky dummy. You only need to do this once.

I had to set up the command blocks in a very specific pattern for them to work, as shown:

I think this has something to do with how command blocks handle firing off "simultaneously". The comparator in this setup is in subtraction mode, creating a "comparator clock" which pulses very quickly.

The command blocks on the left are your scoreboard related commands. The one on the bottom left sets "sneaky" to 0 for all players:

/scoreboard players set @a sneaky 0

The command block on the top left sets "sneaky" to 1 for all players with the stealth boots equipped:

/scoreboard players set @a sneaky 1 {Inventory:[{Slot:100b,tag:{display:{Name:"Stealth Boots"}}}]}

The command blocks on the right are your effect commands. They give players the invisibility effect, or take it away, as appropriate. The one on the bottom clears the invisibility effect from all players without the stealth boots:

/effect @a[score_sneaky=0] 14 0 0

The top one gives the invisibility effect to all players with the stealth boots:

/effect @a[score_sneaky_min=1] 14 30000

This can be done without a scoreboard in 1.13, which added a "nbt=" selector argument:

/effect @a[nbt={Inventory:[{Slot:100b,tag:{display:{Name:"Stealth Boots"}}}]}] minecraft:invisibility 30000 200