Question: The Invisibility spell reads thus:

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> A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person. **The spell ends for a target that attacks or casts a spell.**
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This doesn't specify whether it refers to taking the Attack action, or rolling an attack roll. I thought this usually defaulted to making an attack roll, but, [this answer](https://rpg.stackexchange.com/a/103511/16395) claims that if you take the Ready action, the Invisibility spell would not end, since it's not an Attack action or a Cast a Spell action.

Is that a correct reading? It seems to clearly be against RAI at least, if not also against RAW. What would stop someone from taking the Ready action with a condition that basically immediately resolves? For instance, I could choose as the perceivable circumstance, "when I feel the ground beneath my feet" which is true already, so would trigger right away. Then you could attack or cast a spell as normal.

Wouldn't this make the Invisibility spell not much different to Greater Invisibility? Sure it uses a reaction and probably means you can't use an extra attack... but it still seems a bit wrong.

Answer: 
You can ready one attack without breaking invisibility, but not a spell.
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Readying an action allows you to use your action to act outside of your turn. This allows you to ready an attack action which you will execute later. Once you do execute it, you will have made an attack and will break invisibility. Note that it doesn't matter if you make your attack using the Attack action or any other feature.

Readying a spell is a different story, the rules for readying an action state:

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> When you ready a spell, you cast it as normal but hold its energy, which you release with your reaction when the trigger occurs.
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Since you need to cast the spell right away in order to ready it, you will break invisibility immediately.

**Balance concerns**

The ability to make a single attack before breaking invisibility doesn't break anything since you could do that simply with a regular Attack action during your turn.
You totally can ready the Attack action, which as it is not an attack or a spell, won't break invisibility.

However, as soon as you use your reaction to attack, you *are* attacking and you will therefore lose your invisibility. Note that in the description they say 'attack' to mean any sort of attack, not just the Attack action so other things that your DM considers attacks would break your invisibility.