diff --git a/fs_edit_preconditions.lua b/fs_edit_preconditions.lua
index 9ee39b5..0d8a6a1 100644
--- a/fs_edit_preconditions.lua
+++ b/fs_edit_preconditions.lua
@@ -1,6 +1,35 @@
+-- TODO: check inscription of a sign?
+-- TODO: invlist as dropdown of inventory lists at detected position
+-- TODO: variable as dropdown of allowed variables
+
+-- Which diffrent types of preconditions are available?
+-- -> The following fields are part of a precondition:
+-- 	p_id		the ID/key of the precondition/prerequirement
+-- 	p_type		selected from values_what; the staffs allow to use other
+-- 			types like "function" or "has_item" - but that is not
+-- 			supported here (cannot be edited or created; only be shown)
+-- 	p_value		used to store the subtype of p_type
+--
+-- a state/variable:
+--	p_variable	TODO
+--	p_operator	selected from values_operator
+--	p_var_cmp_value can be set freely by the player
+--
+-- a block in the world:
+--	p_pos		a position in the world; determined by asking the player
+--			to punch the block
+--	p_node		(follows from p_pos)
+--	p_param2	(follows from p_pos)
+--
+-- a trade defined as an action: no variables needed (buy and pay stack follow
+-- 			from the trade set as action)
+--
+-- an inventory:
+-- 	p_itemstack	an itemstack; needs to be a minetest.registered_item[..];
+-- 			size/count is also checked
 
 -- some helper lists for creating the formspecs and evaulating
--- the player's answers
+-- the player's answers:
 
 -- general direction of what a prerequirement may be about
 local check_what = {
@@ -77,23 +106,6 @@ local check_variable = {
 }
 
 
--- TODO: check inscription of a sign?
--- TODO: invlist as dropdown of inventory lists at detected position
--- TODO: variable as dropdown of allowed variables
-
--- which diffrent types of preconditions are available?
--- possible variables:
--- 	item		an inventory item or block (check if it exists)
--- 		-> needs to be a minetest.registered_item[ item ]
--- 	text		some text
--- 	pos		a position in the world (not too far from the NPC)
--- 		-> determined by punching
--- 	variable	name of a variable
---
--- TODO: may all boil down to automaticly setting some lua code?
---       -> better write a function for each one that can be called when needed
-
-
 -- returns a human-readable text as description of the precondition
 -- (as shown in the edit options dialog and in the edit precondition formspec)
 yl_speak_up.show_precondition = function(p)