Handling Passive Skills in 5e and other rulings.

After the game +Joshua Macy and got to talking about 5e rules. In general my approach to go with the book unless it doesn't make sense as if you were really there. With magic and other fantastic elements the object to be consist both from session to session but also with the expectation of how powerful the element should. For example a first level spell should feel like a first level spell. If it feels like a fifth level spell then likely it grants too generous of a benefit.

After the game Joshua and I talked about the Web spell. Particularly when to make the Dexterity Saving throw to see if you are restrained.

First the section in question

Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw. On a failed save, the creature is restrained as long as it remains in the webs or until it breaks free. 

A creature restrained by the webs can use its action to make a Strength check against your spell save DC. If it succeeds, it is no longer restrained.

The discussion was over what does enters them during its turn really mean. Does it means only went you first enter the spell's area of effect? In which case making your dexterity saving throw means you freely can move throughout the web until the beginning of your next turn. At which time if you are still in the web you need to make another save. Or does it mean for each step, 5 foot, etc) you make in the web you make a dexterity saving throw. And if it is the latter is that make it too powerful for a second level spell?

My personal opinion and the way I been refereeing it is that you make the saving throw for each 5 foot step you make unless it takes you outside of the web. I can see how the wording could lead people into thinking it gives a free pass for one round of combat. But in my view that goes against what you would be seeing if you are there. The character is in the midst of sticky webs. Unless he talking step to a clear area he running into the same problem with every steps as if he was first stepping in the first place.

Also downside of failure is beign restrained. Which amounts to you not being able to move and all your attacks being at an disadvantage. While this sucks for the character it doesn't leave him out of options or the means to defend himself. This along with everything else makes web seem like a useful 2nd level sleep but it not a game over for combat.

When I compare it to the classic DnD version of web I am very comfortable with 5e web working this way.

Then Joshua pointed out that Mike Mearls had a AMA session on Reddit. That it contained a clarification of how passive skills worked.

Any skill can be used passively - it's up the DM to apply that as needed. For perception checks, you passive result is always in effect. If you could see something with a DC 10 check and your passive is 11, you see it without rolling. Keep in mind, though, that a DM might rule otherwise. Passive checks are a tool that groups can use to speed up the game or move past die results that slow things down or lead to a grind.

This some great stuff! Despite my years of experience with GURPS and other skill based system I was confused about the distinction between passive and active use of the skill. After reading this, I now have a way that will work for me.

If you are in combat, in a situation where the result of failure is significant, or you only get one shot at completing the task, then you roll as normal your ability or skill versus the DC.

However if you do have the time and there no other pressure or circumstance then you make a roll but the lowest you can roll is your passive score. And if you passive score is higher than the DC you automatically succeed. If you fail you can repeat the attempt but realize that each attempt takes about a turn (10 minutes) so you will be racking up wandering monster checks and any other consequence spending a lot of time in a particular area.

I realize this isn't quite what Mearls said but I used elements of this for the ability system I use when running with my Majestic Wilderlands supplement. In fact along with the advantage/disadvantage I might adopt this as the default regardless whether I run MW or 5e.