@BwdYeti
Properties and variables in the RPG modules are always accessors.
@kirbywarrior
I think Juno's method is the best. It's easily doable with a script but, unless you need to change the descriptions of 1000 items, it's easier and more efficient to do what Juno sais.
But if you really want to do it with a script, here's what I would do:
I would start by adding 3 description hashes to game system (for item/weapon/armor).
Then I would cycle through all Items Data and add their descriptions to the hashes:
@item_description = {}
@weapon_description = {}
@armor_description = {}
for item in $data_items
 @item_description[item.id] = item.description
end
for weapon in $data_weapons
 @weapon_description[weapon.id] = weapon.description
end
for armor in $data_armors
 @armor_description[armor.id] = armor.description
end
These variables must be accessible from anywhere so make them attr_accessors.
You need to add this just before
def initialize
attr_accessor :item_description
attr_accessor :weapon_description
attr_accessor :armor_description
Then, I would modify the RPG::BaseItem class by adding 2 methods. One to reads the description and one to modifies it:
def description
 return @description if $game_system.nil?
 case self
 when RPG::Item
  if $game_system.item_description[@id] != nil
   return $game_system.item_description[@id]
  end
 when RPG::Weapon
  if $game_system.weapon_description[@id] != nil
   return $game_system.weapon_description[@id]
  end
 when RPG::Armor
  if $game_system.armor_description[@id] != nil
   return $game_system.armor_description[@id]
  end
 end
 return @description
end
def description=(string)
 @description = string
 return if $game_system.nil?
 case self
 when RPG::Item
  $game_system.item_description[@id] = string
 when RPG::Weapon
  $game_system.weapon_description[@id] = string
 when RPG::Armor
  $game_system.armor_description[@id] = string
 end
end
Now, if you do it right, it should be working. The only thing you need to do to change an item's description is to use
$data_items[id].description = "my description"
$data_weapons[id].description = "my description"
$data_armors[id].description = "my description"
I did that in 20 minutes, on wordpad, at work. So it's possible that you encounter a few errors.
If you need me to clarify, feel free to ask!
Take care!
-Dargor