How specific does the Action for Ready need to be?

Question

Starting with the rules for the Ready action:

Sometimes you want to get the jump on a foe or wait for a particular circumstance before you act. To do so, you can take the Ready action on your turn, which lets you act using your reaction before the start of your next turn.

First, you decide what perceivable circumstance will trigger your reaction. Then, you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it. Examples include "If the cultist steps on the trapdoor, I'll pull the lever that opens it," and "If the goblin steps next to me, I move away."

When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger. Remember that you can take only one reaction per round.

My question centers around the "choose the action you will take". How specific does this need to be? Are you literally just choosing one of the standard action choices ("Attack", "Help", "Hide", etc.), or do you need to specify any "parameters" or "targets" or the like for the action you will take?

To try to make this a bit more concrete, could I ready an action for "When the Goblin moves, I Attack", and then when the trigger happens I can choose whether to attack the Goblin or the Bugbear, and what weapon I'm using? Or do I have to give those details up front as part of specifying the Ready action? Other actions like Search and Help similarly have details that need to be given in order to really be, well, actionable, and it may be useful on occasion to defer the specifics until the trigger actually happens.

Shedding some light and some confusion on the issue is that Cast a Spell has its own special rules for being readied, but I don't know whether to treat that as a precedent for specifying details up front (since presumably you need to at least specify which spell to be able to "hold its energy", though I don't know about details like spell slot or targets), or whether it's a case where it's a specific rule specifically because because it's different from the general rule.

Related but different questions:

• How specific does the trigger for a readied action have to be? (But I am asking about the action instead.)
• Can the action in a Ready Action be conditional? (But that is about choosing a different action at the time of the trigger, whereas I am asking about a single Action choice but when the choices for the details of that action are made.)

Answer 1

You must choose an action or movement, but you can omit other information.

Then, you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it.

As we can see from this sentence, the minimum requirement is to choose an action or movement. I believe "the action" in this context is anything from Actions in Combat which includes:

one of the actions presented here, an action you gained from your class or a special feature, or an action that you improvise. Many monsters have action options of their own in their stat blocks.
When you describe an action not detailed elsewhere in the rules, the GM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure.

So for instance "If X happens, I attack" and "If X happens, I use channel divinity" meet this requirement, whereas "If X happens, I do something" is not specific enough.

The PHB also gives us some examples from which we can make additional inferences:

1. If the cultist steps on the trapdoor, I'll pull the lever that opens it
2. If the goblin steps next to me, I move away

The first example is very specific.

In fact, there isn't any relevant information that we could add to "I'll pull the lever that opens it" to make the Ready action more specific: we can pull that one lever that opens the trapdoor mentioned in the trigger, and even if other levers were present we wouldn't be allowed to pull them.

The first example also shows us that we can choose an action implicitly, because in this example we chose the Use an Object action without naming it explicitly.

The second example is very vague.

There is plenty of relevant information that is missing from "I move away", such as whether we will walk, swim, or fly, and which path we will take. Therefore, the second example confirms that we can be vague and omit relevant information.

However, even this example is not completely devoid of relevant information, as "away" implies a general direction. This suggests that it's best to include at least some relevant information.

Moreover, eventually we must choose whether to walk, swim, or fly, and which path to take. So if our Ready action is vague we can make decisions during the reaction.

Your example.

You can ready an action for "When the Goblin moves, I Attack" as this meets the minimum requirement for the Ready action.
Because that Ready action omits relevant information, you must make decisions during your reaction, such as who to target with your attack(s) and which weapon to attack with.

In particular, you could choose to attack a Goblin, a Bugbear, or anyone else for that matter. However, you cannot unsheathe a weapon during your reaction because you can only use your free object interaction "during either your move or your action", which means that your choice is limited to the weapon(s) that you are wielding when the Goblin moves.

Answer 2

My reading on Rules as Written

The rules are, as you observed, unclear about it, which leaves us with... Up to the DM. Now, from how I read/understand it:

Everything on the readied action must have been decided the moment you readied it. In particular for your example, "I attack" is not a (complete) action; "I attack the goblin" or "I attack the Bugbear" are (as long as other details, such as "with which weapon?" can be deduced from the context, e.g. the person is only holding one weapon - otherwise these details also should be specified). This is backed by the reading

Then, you choose the action you will take in response to that trigger

and

When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.

Note that nowhere it states that you can make any change or add any detail to the action you are taking when the trigger happens - or when you take your reaction. You either take the action you described earlier (without any modification to it) or you ignore the trigger. From how I understand it, that means you can't simply change your action from "I attack" to "I attack the Bugbear" mid-way.

The main point here is: you can not add any further detail for the action after you have described it when taking the Ready action. Or, at least, there is no rule that allows it explicitly, thus my reading is that it is not allowed.

Comments suggested that the "If the goblin steps next to me, I move away." example from the book needs more clarification, so clarification should be possible to be made during the reaction. First, I disagree with the premise - given (any) context, this action seems pretty clear for me. Second, I wouldn't try to extrapolate an example for a more general ruling, specifically one with arguably more mechanical impacts than what the example provided.

For explaining better this reading, the intention for the ready action seems to be to delay an action that you could take in your own turn. If you simply said "I attack" as an action in your turn, your DM would simply ask "Who?" and "With which weapon that you are holding?". If you say "I get ready to attack", I would ask the same questions.

Extrapolating Crawford's words

When answering about the trigger, Crawford states (thanks Isaac Reefman for this one)

Ready action: the trigger should make your intent clear. If you say, "I attack the first enemy I see," only one enemy will qualify.

While we should be careful on extrapolating tweets from Crawford, assuming the same applies for the action, i.e., the action should make your intent clear as well, seems fair enough for me.

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For the Cast a Spell rule you mention, it is a specific rule for the spell case. It does not set and should not be used to set a precedent for the general rule. I have made the same mistake before. But for that case, you need to specify the spell slot and the target, as when you ready the spell, you are already casting it (reason you lose the spell slot even if the trigger doesn't happen), you simply are not releasing it yet. Spells require the target for you to cast them, not to release them.

Answer 3

You need to be as specific as your DM requires

Readying an action is like creating a rule. You supply the trigger and the action you take. If the action cannot be taken, then you can't take it. You can also choose to ignore the trigger. In that sense, a trigger and the action must be as specific as you need it to be. If you say "When the goblin moves, I attack", your DM is going to decide what exactly that means. Are you being very literal? Are you being vague on purpose? Either your DM will decide for you, or you will need to clarify. The bottom line is you are entering a contract with your DM based on terms you both should agree on, and the contract can't be changed after it is agreed upon. It really depends on your DM's style of play. Your DM is capable of rewinding time if you really disagree or misunderstand the contract you've written.

This happens with every action in the game. You declare an action, your DM decides what happens. Usually the DM needs more info, they will ask for it. An action like "I attack" may very well be specific enough. Attacking involves choosing a target and can normally involve drawing a weapon as part of that action. If your DM doesn't like this kind of freedom, they may ask you to clarify with which weapon and which target.

In short, be as specific as you want to be with your action. If you want to be as vague as "When he moves, I attack", then be that vague. If you want to be as specific as "When this goblin takes one step back, i want to draw my bow and make a ranged attack with my bow on that goblin", then be that specific. There are no other rules governing how specific you must be.