Do ability checks in combat require an action?

Question

I was under the impression that using skills, and therefore making an ability check in combat required an action. Note: I'm obviously not talking about passive perception, it's definitely passive, it's got passive in the name.

But, like, say, while in combat, if a player tries to bluff a Giant, or examine an illusion to see if it's real, that requires an action. Doesn't it?

I'm happy to admit I'm wrong, as I'm having a hard time finding any kind of citation for that, aside from the context of various illusion spells which specifically state that one must take an action to examine the illusion and perform an intelligence check in order to reveal it as fake. But wouldn't most of the other skills that involve you doing something, or taking time to think about something, be in the same boat?

Answer 1

Often, but not always

Many ability checks in combat require Actions, and many Actions require ability checks. Unambiguous cases are spelled out in the section on Actions in Combat (PHB, p. 192-193). For example, the "Hide" or "Search" actions both require ability checks, and both take up your Action (unless you have a special feature which allows you to do them some other way).

However, not every ability check in combat requires your full Action. A prime example is grappling. (PHB, p. 195, bold added)

When you want to grab a creature or wrestle with it, you can use the Attack action to make a special melee attack, a grapple. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.

The target of your grapple must be no more than one size larger than you, and it must be within your reach. Using at least one free hand, you try to seize the target by making a grapple check, a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use).

In this case, we have two ability checks which do not require a full Action. One on the part of the grappler, which requires the use of one of their attacks, and another on the part of the target of the grapple which requires no action, reaction, or movement. (Of course, the grappler had to use the Attack Action to be able to grapple at all, but the ability check to grapple did not use up the entire Action).

Another example is found in the spell Tsunami (PHB, p. 284, bold added):

A creature caught in the wall can move by swimming. Because of the force of the wave, though, the creature must make a successful Strength (Athletics) check against your spell save DC in order to move at all. If it fails the check, it can’t move. A creature that moves out of the area falls to the ground.

If this check required an action, the spell's description would say so. Contrast this with the description found in the spell Wrathful Smite (PHB, p. 289, bold added):

As an action, the creature can make a Wisdom check against your spell save DC to steel its resolve and end this spell.

Does it take an Action? DM decides

As a general guideline, it's heavily implied that more difficult activities require actions: this is especially stressed in "Other Activity On Your Turn" (PHB, p. 190, bold added):

The DM might require you to use an action for ... activities when it needs special care or when it presents an unusual obstacle. For instance, the DM could reasonably expect you to use an action to open a stuck door or turn a crank to lower a drawbridge.

And it's understandable that you would think that all activities that require ability checks require an Action. After all, the definition of ability checks states (PHB, p. 186, bold added)

The DM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure.

But this definition states "when you use an action that could fail, it requires an ability check": the converse, "when you use an ability check, it requires an action," is not necessarily true. If you attempt something in combat which is defined as taking an action and requiring an ability check, then it definitely requires both. Otherwise, the sections on both "Other Activity On Your Turn" (PHB p. 190) and "Improvising an Action" (PHB p. 193) leave the decision up to the DM when to call for the use of an action, the use of an ability check, both, or neither.

Answer 2

There is no such general rule

First, a character cannot "make an ability check". They act as the player describes them and the DM calls for rolls if necessary (guidelines: DMG 237). Whether something requires an Action to do and whether a successful check is necessary to do it are completely separate questions. There is no rule stating that if you have to roll an ability check, doing so also consumes your Action.

Answer 3

Examples of skill checks that don't require an action

(all from the Basic Rules)

Athletics: hold onto a surface while someone tries to knock you off; resist being grappled; swim against a current.

Acrobatics: keep your balance on the deck of a rocking ship.

Animal Handling: keep your mount from being spooked.

Insight: notice when someone is being dishonest.

Survival: avoid an environmental hazard.

Deception: maintain a straight face while telling a lie.

Persuasion: exhibit proper etiquette.

and, since you said "ability checks" generally,

Initiative.

Answer 4

RAW - Yes.

While your DM can make exceptions based on the circumstance, using a Skill is generally considered an Improvised Action.

Improvising an Action

Your character can do things not covered by the actions in this chapter, such as breaking down doors, intimidating enemies, sensing weaknesses in magical defenses, or calling for a parley with a foe. The only limits to the actions you can attempt are your imagination and your character’s ability scores. See the descriptions of the ability scores in chapter 7 for inspiration as you improvise.

When you describe an action not detailed elsewhere in the rules, the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure (PHB 192)

Aditionally, if you read further down the page, you have the "Search Action" which states:

When you take the Search action, you devote your attention to finding something. Depending on the nature of your search, the DM might have you make a Wisdom (Perception) check or an Intelligence (Investigation) check. (PHB 192)

This shows doing things that result in ability checks is considered to be an Action. (In this case, Searching is an Action that leads to the Perception/Investigation roll.) Anything you do can prompt a roll resulting in using your Action for a Skill.

RAI (Rules as Interpreted) - Not Always.

You can still get away with prompting passive checks if you're not actively trying to do something. For instance, "What do I see?" generally prompts your DM to tell you what all you see in the area based on your passive score. You can apply this method to other skill checks, but remember, your DM may make you use an action if you do this too often or if you word it in a way that can be taken as an active Action.

How I do it:

When a player wants to do something, depending on the request, I may allow them to do it as a Bonus Action instead of using their Action at the cost of them rolling with disadvantage and only being able to do stuff for a more generalized result. Example Scenario:

They're in the crypt of Willkaiser the Bloody. There are vampires everywhere and their party has been split up, flanked from every side. In front of Christoph, the Bard, stands Willkaiser himself with a bemused smile on his face and a ravenous hunger in his eyes.

Example Rolls Christoph may Ask:

How many vampires are there?

Do you want to know exactly or do you want a general idea?

1. Exactly.

   As an Action, roll me Wisdom(Perception).

2. Give me a general idea.

   As a Bonus Action roll me Wisdom(Perception) with disadvantage.

   Fails: There seem to be quite a few, but you don't feel safe looking away from Willkaiser to get a better idea.

   Succeeds: There seem to generally be between 3 and 5 vampires near each of your allies. You could try and get a better look, but that would cost using your Action to find out more.

I hope this gives you an idea of how you can make creative use of Skills as more than just Actions without having to make your players always waste their Action on it. This is just how I do it, and there is no right or wrong method. (I've seen DMs who treat Skill checks as free actions, so long as the player only does one per turn and doesn't do it constantly.) Just do what feels right for you and your campaign/party.