Possible Accuracy Descriptions

S++: You are taking this damage unless you have a hastened dodge and a good plan. Examples include???

S+: The attack is ambiguous and very hard to interfere with. Usually there are very few ways to defend against this attack without taking damage. Examples include large-area boss attacks

S: Attack is ambiguous, and very hard to dodge. They are frequently altered and influenced by other factors, but basically impossible to dodge normally. Examples include debuffs and healing effects.

A+: Attack is well-aimed and instantly hits. Even small targets are easily hit, but dodging is still effective.

A: Attack is easy to aim and difficult to dodge. Examples include cannon shots, and other attacks that hit instantly. Dodging is useful against these attacks, and they are generally clearly attacks.

B: Attack is easy to aim and hard to dodge, but it is easy to position yourself so you cannot be hit. Examples include swords which will almost always hit adjacent opponents (though the opponent can move from being adjacent), and boomerangs which only hit across a very specific path. Dodging is moderately effective against these attacks, and they are prone to interference from other factors.

C: Attack is easy to aim, but also easy to dodge. Attacks will generally hit reliably against a stationary target, but will almost always miss a target that is intentionally dodging the attack.

D: Attack is very hard to aim and easy to dodge. Attacks will not hit reliably, especially if the target has dodged this turn. Dodging the attack specifically means it will almost always miss.

I feel these are important to give players an idea about why dodging is important and will give them better guidelines for what works when. Additionally, it will give a good reason for pure status effects to be more useful against many targets.
Note: There are no "+" accuracy, the letters are the only thing that can mark the accuracy level.

Also, the accuracy can be heightened/lowered along with the quality of the RP. So there is a possibility that even if you use a S rank chip, there is a chance of failure.
Bad example. S rank means 100% accuracy which is why it is attributed to healing chips and certain rare to-all chips. They are never supposed to miss.

"Even an A-rank accuracy gun attack with lock-on and a take aim action being used by a cursor navi targetting an immobile enemy can miss" would be a better example.

Anyways, Goroke's point stands that the letter grade accuracy is mainly just a guideline (though we do use numbers). RP is a large part of it so we don't want people growing too dependent on certain descriptions and arguing that they should have hit because some letter implied it was a surefire thing.