[RPG] When to use skill checks in social situations with NPCs

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I'm new to DMing and I've been planning my first adventure (for D&D 5e). However when it comes to non-combat situations I don't know when it makes sense for a skill check to be used or when the NPC would just reply.

Best Answer

To answer this question, we need to first consider how D&D handles actions. It usually goes something like this:

  1. GM describes situation.

  2. Player declares action.

  3. GM determines whether player needs to roll check.

  4. Player rolls check if necessary.

  5. GM describes outcome.

The step you are having difficulty with is step 3.

Ability checks tell us whether the character is able to perform a certain task, whether that task is jumping over a ravine, or persuading the king to give him command over a few soldiers. Some GMs like to use ability checks to determine something about their world. That is to say, if you fail to pick the lock, that means that that particular lock is too difficult for your character (i.e. you can't just try again). Others like to see each ability check as just an attempt by the character (i.e. you can try again).

Regardless of your approach, there is one thing in common: a possibility of failure. If there is no possiblity of failure, then there is no need for a check, since whatever the player rolls, their character will still succeed. For example, if the player wants to persuade the innkeeper to let them buy a meal, there is no chance that the innkeeper will say "No, I don't want your money." Therefore, in that situation, no check is needed, you just let them succeed immediately.

What if the chance of failure is 100%. That is to say, the character has no chance of succeeding at all. For example, perhaps a player wants to try to jump across a 100m chasm - that's impossible. In that case, whatever the player rolls (even a natural 20) should fail. There is therefore no need for a check, you just tell them that they failed immediately. However, when this happens, there is usually some misunderstanding. If the character is trying to jump across a 100m pit, it's pretty safe to say that that player thought that the pit was much narrower. For this reason, a good policy is to explain that such an action would be impossible before adjudicating the result: "You do realise that that pit is 100m wide right? There's no way your character can jump across."

With the above in mind, let's expand step 3:

  1. Determine whether the action has a chance of success. If it does, move on to step 2. If it does not, tell the player that the action is impossible (when appropriate). If they still want to try, describe the consequences of their failure.

  2. Determine whether the action has a chance of failure. If it does, move on to step 3. If it does not, tell the player that they succeeded, and describe the consequences.

  3. Determine how difficult the action is. There is a nifty little table on page 238 of the DMG to help with this. This table is also on the official DM screen. if you find yourself choosing "very easy" or "nearly impossible", then you might want to reconsider steps 1 and 2 to see if you should call for a check at all.

  4. Tell the player to roll the check. Whether or not you like to tell them the DC in advance is up to you.

Once you get practised with this, it becomes almost instinctive. For now though, you might want to think about it in steps as I outlined.


I'm now going to address the idea that checks should only be called for when failure is interesting.

Let's imagine a situation in which the character are climbing up a ridge. Suddenly, the bit of rock that they are clinging on to falls off the cliff face. If they fell to the bottom, they would immediately die (a TPK). It could be argued that failure here is not interesting, so you should just let them somehow save themselves. However, it should be obvious that this is almost impossible. At this point, the players begin to feel that your world is not consistent. That can really harm your game, as players base all their actions on the idea of a consistent world.

Another example would be the tight-rope above pillows. The question is this: Why did you include it in your adventure? If you want the characters to succeed on something, then make it so easy that they can't fail to succeed first time.

What you have there is a problem with your adventure design. You should design your adventures (or run modules) in such a way that, if there is a chance of failure, then it is interesting. If you are running a murder mystery, don't have the whole thing hinge on one clue, otherwise what happens if the players never even go to the place where they can find it? Instead, sprinkle clues liberally, all pointing to the same place. The players will miss one and misinterpret another before finally working it out (although that's somewhat of a cliche).

Finally, if for some reason the player's have failed the entire adventure, let them. If they always succeed somehow because you fudge things, there is little sense of accomplishment when they do succeed. But, you must have a way to signal to them that they have failed, otherwise they will keep banging their heads against the wall.


As a final addendum, I strongly recommend that you check out The Angry GM's how to GM section. There is so much good stuff there about how to run games, adjudicate actions, run combat, etc. I have found it immensely useful. He seems to be pretty much the only person on the internet who codifies GMing into easy to follow steps, rather than assuming that all GMs know exactly what they're doing.