Let’s toss out some disclaimers before I start voicing my opinions, as it’s a good thing a responsible contributor ought to do.

Mechanics are important, they are the lifeblood of any game. That’s just facts. Otherwise we suffer the “power level” syndrome where things consistently escalate in order to impose a challenge.

What most define or refer to as the “Rule of Cool” is the implied suggestion that a game master within their power allow for actions or results that typically (though not required) irregular to the mechanics, so long as it facilitate the vague criteria of “that’s cool”.

I’ve run games and have played many games more than anything, not just D&D, I’ve had a rainbow colored history of tabletop role playing systems. It’s a tough call sometimes for both a game master and even a player to push the boundaries of the mechanics of both their characters and the environment (or setting). Sometimes it can become abusive from both directions, the players may learn of a useful trick with the mechanics and it eventually becomes an exploit that ruins the game. Or sometimes the game master is so strict with the narrative and/or mechanics that the players feel confined with their choices.  There is also the situation where the game is extremely vague that the players and the game master are lost on what direction to take the game (whether narratively or mechanically). Even I tread lightly with my tightrope, you want everyone to have fun and a good experience since it’s a shared experience.

“You’re the lead writer, the players are the team of writers”
My outlook on gamemastering is generally with the mindset that I’m the Lead Writer for a tv serial, with the players as the contributing writers regarding their characters and any dynamics relevant. The responsibilities are shared more or less depending on the system. But the most important aspect to always keep in mind, while the game master often embodies the roles of foes and enemies, an adversarial role or mindset often is attributed to those in the position. Adversarial quirks can keep the players entertained and fearful of what dark plots you have in store for them. But the game master should not undermine the creativity or the routes the players wish to take, at least not without some exceptions. A GM is the referee as well, you call the plays and resolve them. In essence, you are the bar that establishes what is within acceptance in regards the players’ actions, that does not necessarily mean you have to always say “no” but know when to use it.

“Saying ‘No’ is OK”
I am from that school of gamemastering where you try to say “yes” as often as possible when your players ask if their characters can do an action, often times it’s an action or use of an ability that either does not coincide with the intent or actual application of said ability or action. But I try and not infringe on that creativity often, I often will compromise with the player on a reasonable alternative if I deem the action excessive to the capabilities intended. But there plenty of times when the situation calls for a simple “no”. Some game masters are afraid of using this phrase, as it may be a hinderance on creativity or ideas. But keep in mind what was stated earlier, you’re the referee for your players in relation to the rules and gameplay, there needs to be a precedence for expectations between the players and their game master.

If the players do not know what to expect from their game master, it becomes increasingly difficult if not frustrating to suggest ideas or points of interest regarding their actions or narratives. The same can be said for game masters or dungeon masters, it’s equally important that the ones running the game have a set of expectations from their players, it’s imperative for the players in this venue that they know what their game master wants or anticipates from the players.

When I began our journey with my friends for our game, I made it clear what I was expecting from them, and since they never played a tabletop roleplaying game prior I gave them examples of what players typically expect from their DMs. We have adjusted them over time but generally the original core principle remain intact. Which brings us to the next important tidbit.

Communication is key. It sounds repetitive but bares repeating.
I cannot stress how important it is for the players and the game masters to communicate, either for problems or for ideas. The act of playing in a tabletop roleplaying game is that everyone is involved in this shared narrative. I played for many years on play-by-post forums, I will have to say that the more successful and lengthier games were often the ones that came from the ones where the GM was regularly in communication with the players and vice versa. Granted the nature of play-by-post forums eventually led to games that never reached an end or conclusion, feeding to a never-ending desire to play more games. But I digress.

I can use my own personal experience here, I’ve had instances where I had to take on burdens that I did not actually desire or want. But I decided to not voice my opinions and ran with whatever I deemed would make my players’ happy. Ultimately I learned that the burden turned into frustration and led to a miserable experience. Honestly, I learned from that experience (even though I sometimes end up with a similar situation every once and a while) that it’s MY game. Granted it’s a game I play with my friends, but it’s a game I chose to run with my friends and in particular, friends I wanted to play with together. I would say that the next important thing to recognize is one’s limits both in game and out of the game.