What is technically considered an attack?

[Theodoxus]

Is Viscious Mockery an attack?

It's battery, so yes.

Also keep in mind that most spells that fall under the latter category also specify "an attack or any harmful spell", so the Fireball would count. But if it doesn't specify that harmful spells also count, then by RAW, they don't.

Then it falls into the category of "we need to explicitly write 'this is an attack' on everything that could be construed as an attack. Why the editors / layout manager felt it was ok to expand the Index to include every reference of "X, see Y" instead of "X page Y" and yet couldn't be bothered to denote every instance of attacks or 'not-attacks' is beyond me.

Since RAW doesn't specify everything in a binary fashion that X is an Attack while Y is not an Attack, we only have RAI to go on. So, easiest to conclude, even if it flies in the face of Crawford and his lack of foresight - that if it's considered battery, it's considered an attack. If it's an assault with no battery, it's not an attack and thus doesn't break spells that break on an attack.

Perhaps a project would be to either go through every action and determine if it's an attack or not, or go through every spell that says it breaks on an attack and change "attack" to "battery". I know which would take a LOT less time to do...