Implicitly taking - only works for existing actions?

Zapping it with is an action applying to two things. Understand "zap [something] with [something preferably held]" as zapping it with.

Before zapping something with when the player does not carry the second noun:
	carry out the implicitly taking activity with the second noun;
	if the player does not carry the second noun, instead say "You'll need to be holding [the second noun] first."
Report zapping it with: say "You zap [the noun] with [the second noun]."

Testing is a room.

The target is scenery in testing. A wand is in testing. 

Test me with "zap target with wand/take wand/zap target with wand".

The implicitly taking activity doesn’t seem to be carrying out the standard behavior (as documented in section 17.32). There’s only one example which carries out implicitly taking for a new action, and that is Ex 420 (in section 20.10). That example creates a new “Rule for implicitly taking while multiply-giving”. Is such a rule necessary for every action you might define (that requires implicit taking)?

You’re not supposed to carry out that activity at all. (I don’t know why it’s in that example.) It’s a hook for you to modify the parser’s default behavior, which is built into the parser.

Implicit taking occurs when you specify an action as applying to “a carried thing”. So you really just want this:

Zapping it with is an action applying to one thing and one carried thing. 
Understand "zap [something] with [held]" as zapping it with.

Get rid of the before rule (that prevents the implicit take from ever happening) and the “something preferably held” (that’s just a disambiguation bias, which you probably don’t need unless “zap wand with wand” is a likely command.)

OK, that makes sense. I was misled by the example, then.

An overly elaborate explanation of implicitly taking in example 420 is below the spoiler.

[spoiler]The reason the rule for implicitly taking is in example 420 has to do with the behavior of actions that can apply to multiple things, like “take robe and wizard hat.” A command like that is processed as two separate actions: take robe and take wizard hat, which generally print their own response:

But the multiply-giving action in example 420 is meant to accommodate commands like “Give dollar and pie to morgue attendant,” where giving the dollar and pie together can have different results than giving it separately. So the example goes through a lot of complicated machinery to take the action of multiply-giving the dollar and the action of multiply-giving the pie and turning it into something that has to do with the list {dollar, pie}. In the particular case of implicitly taking, it doesn’t want to announce (first taking the dollar) and then (first taking the pie). Instead, every time it performs an implicit take, it adds the items you took to a list (which it calls the recently-collected list), and at the end it prints out something that deals with the whole recently-collected list all at once. (“You pick up [the recently-collected list] and make your offer” or something like that.)[/spoiler]

So basically, you don’t need to worry about that, unless your new action involves doing weird stuff with multiple items.

I didn’t know there is a difference between “something preferably held” and “held” or that “held” is a valid grammar token!