Code (Skript):

1. on rightclick:
2. player's tool is red dye named "&5Health Crystal":
3. heal the player by 5 hearts
4. damage the player's tool by 5
5.  

I think this will work but I'm not sure
You should use an item that can receive damage or something like that.

 

it might be possible, but it will be complex.

 

Code (Skript):

1. on right click on player holding red dye:
2.     heal the event-entity by 5
3.     damage event-player by 5

 

Oof I was trying to make it, it was so complex for me. I even decided to use Skript-mirror.

and it's that simple.... damn. You are skilled

 

nah i know the feeling... i tend to overthink things at times too

 

Hi i'm bored so I decided to do unnecessary stuff

Code (Skript):

1. command /hc:
2.   trigger:
3.     give player 1 red dye of protection 5 named "&5Health Crystal" # with lore "&dHeal a player by right clicking on them"
4.  
5. # One time use
6. on right click on player holding red dye:
7.   if name of player's tool = "&5Health Crystal":
8.     remove 1 of player's tool from player's tool # Supports item stacking
9.     heal the event-entity by 5
10.     damage event-player by 5
11.     send "&5You have healed &d%event-entity% &5using a &dhealth crystal"
12.     send "&5You have been healed by &d%player%" to event-entity
13.  
14. # Cooldown:
15. on right click on player holding red dye:
16.   if name of player's tool = "&5Health Crystal":
17.     set {_waited} to difference between {healthCrystal::%player%} and now
18.     if {_waited} is less than 30 seconds:
19.       send "&cYou are still on cooldown &7(%difference between 30 seconds and {_waited}%)"
20.     else:
21.       heal the event-entity by 5
22.       damage event-player by 5
23.       send "&5You have healed &d%event-entity% &5using a &dhealth crystal"
24.       send "&5You have been healed by &d%player%" to event-entity
25.       set {healthCrystal::%player%} to now
26.  
27. # If using with lore expression within the command
28. expression %itemtype% with lore %string%:
29.     return type: itemtype
30.     get:
31.         set {_item} to expression-1
32.         set {_lore::*} to split expressions-2 at "||"
33.         loop {_lore::*}:
34.             set line (loop-index parsed as a integer) of lore of {_item} to loop-value
35.         return {_item}