Hello!
So recently someone asked me if they were able to Ready action Flurry of Blows. I did some searching and I think the answer is yes. Anyway, that led to a discussion about if we can Ready spells. That led me to wondering if I have been playing my summoner character incorrectly with Act Together. Here's the relevant text (emphasis mine):
Ready: "You prepare to use an action that will occur outside your turn. Choose a single action or free action you can use, and designate a trigger. Your turn then ends. If the trigger you designated occurs before the start of your next turn, you can use the chosen action as a reaction (provided you still meet the requirements to use it). You can’t Ready a free action that already has a trigger."
Act Together: "You and your eidolon act as one. Either you or your eidolon takes an action or activity using the same number of actions as Act Together, and the other takes a single action. For example, if you spent 2 actions to Act Together, you could cast burning hands (2 actions) and your eidolon could Strike (1 action), or your eidolon could use its Breath Weapon (2 actions) and you could Stride (1 action)."
Activities: "An activity typically involves using multiple actions to create an effect greater than you can produce with a single action, or combining multiple single actions to produce an effect that’s different from merely the sum of those actions. In some cases, usually when spellcasting, an activity can consist of only 1 action, 1 reaction, or even 1 free action."
Cast a Spell: "Casting a Spell is a special activity that takes a variable number of actions depending on the spell, as listed in each spell's stat block. As soon as the spellcasting actions are complete, the spell effect occurs. Some spells are cast as a reaction or free action. In those cases, you Cast the Spell as a reaction or free action (as appropriate) instead of as an activity. Such cases will be noted in the spell's stat block—for example, “Reaction, verbal.” "
So it seems like "activity" and "actions" are exclusive terms and not interchangeable. If so, then it would seem that you cannot Ready a 1-action spell because Casting a Spell is an "activity," not an "action." And Ready specifies "a single action." Likewise, in Act Together, it seems as if, for example, your dragon eidolon uses its 2-action Breath Weapon activity, the summoner would not be able to cast the 1-action Boost Eidolon spell because Act Together specifies that "the other takes a single action," and excludes activities.
Am I reading and interpreting this all correctly? It's been nagging at me if they are intended to be distinct, RAW, and if that prevents the Readying of spells and such that I mentioned above. I'm also curious to know how people play it at their own tables and if it's something that's handwaved, or if it's OP to handwave it, etc.