Would using minor illusion warrant more than advantage for a rogue trying to hide?

Question

I am basically a noob when it comes to D&D, but I have taken up the reins for DMing the 5e starter set. The group I am playing with is a mish-mash of some very new to D&D and some who lightly played years ago, and the "seasoned" players wanted to build their own characters, which I am totally down for.

One of the players rolled out a gnome rogue (strange but surprisingly effective build it turns out) and as a gnome he gets the Minor Illusion cantrip.

He was up against a big bad monk, the rogue with 1hp to his name, so used Minor Illusion to create a loud yell just on the other side of his foe. He wanted to distract the enemy monk so he could hide. The monk failed the save so I ruled that the rogue could have advantage on his hide check. He felt like his reward should be something better, but as DM I made a decision and kept the game chugging along, promising to check into the matter more later.

I can't find anything in the Player's Handbook that addresses the question to my satisfaction, other than the DM basically decides. Which brings me to my question: Is there anything in there to support my players plea of "more"?

Answer 1

The spell does exactly as it says; anything further is at your (the DM's) discretion.

If you go strictly by what's written in the handbook, the spell has no mechanical effect whatsoever. It's purely your prerogative as to what effects it has, based on whatever criteria you want.

The most that the rules say about distractions and hiding is this excerpt from the rules for hiding:

However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen. (PHB 177)

Granting advantage is one of the DM's best tools for rewarding inventive player actions, so using it here is an easy choice. Granting automatic success to the hide action would be overkill. Once you've let them get away with that once, they'll use it all the time, essentially turning Minor Illusion into a pseudo Invisibility spell for the rest of the campaign.

Answer 2

As for whether there's anything in the PHB to support your players plea for "more"; well no, there really isn't.
As AgentPaper states, spells work exactly as they say in their description, so mechanically Minor Illusion doesn't really do much, and it's up to the DM to decide what happens beyond that.

Granting advantage on an attack roll or a certain ability check should probably be the most you award a player for creative use of a cantrip though (depending on the situation).
Advantage/disadvantage can be a pretty powerful reward/punishment (especially on a rogue's attack rolls since they have Sneak Attack) but it is not unreasonable for a cantrip to provide such things (see True Strike or Vicious Mockery [note though that True Strike only gives you advantage on the first attack roll and requires concentration]).

Musings on the situation.

Since you can't hide from a creature that can see you (PHB page 177), unless you're using the optional facing rules from page 252 of the DMG and the monster turns it's back on the rogue as a result of the sound, Minor Illusion couldn't/shouldn't directly result in a hide check (even if it's used to distract an enemy).

You should definitely put restrictions on the use of such a reward.
Any (even half) intelligent creature is only going to fall for the same trick once, maybe twice, so having it work only once against a creature, or group of creatures if more than one witness the event, would be advised. Although you can expand/retract that as you see fit.

Minor Illusion doesn't automatically grant creatures saving throws, it requires them to spend an action to make an Intelligence (Investigation) check to determine it's an illusion.
Although I can see the ruling being made that the creature gets a saving throw against being distracted (success would disallow any benefit to the rogue), so if that was your reason, good job.