Quote from Chicken_Champ >>

No he can’t. It’s a special action ranged spell attack granted by casting the spell, not a weapon. 

 Oh yeah, derp.

It's a good spell to use if you're protecting some townsfolk or something.  Stand back with a few of them and spend your turns making stones for them to throw.

Edit: I should say using your BA to make stones for them to throw, and your action doing whatever other attack you want.  You just need 3 random grunts and Magic Stone gives you the ability to make 4 attacks per turn, and can give even the most useless NPC a decent method of attacking from range.
Niche, sure, but powerful when the opportunity arises.

Yes, that would be decent... I suppose you could travel with three hirelings (or Skeletons you’ve raised?) and essentially treat it like an off brand Eldritch Blast by having them use all three pebbles every round? That has potential...

Is the pebble attack a Special Action, or a Use an Object action, do you think? If it’s Use an Object, I suppose a Thief might be able to do it twice per round... and even a Familiar might be allowed to use it????

Quote from Chicken_Champ >>

Yes, that would be decent... I suppose you could travel with three hirelings (or Skeletons you’ve raised?) and essentially treat it like an off brand Eldritch Blast by having them use all three pebbles every round? That has potential...

Is the pebble attack a Special Action, or a Use an Object action, do you think? If it’s Use an Object, I suppose a Thief might be able to do it twice per round... and even a Familiar might be allowed to use it????

 Spell clearly sates that you make a ranged spell attack with it so it would be a standard attack action. No 'use an object' action sneakiness here. Also, I think they would be able to, question is if the familiar has hands to throw them? Maybe a flying one can drop it? with a range of 0 (directly under it like the flying kobolds have)

Being told to make a ranged spell attack is not the same as the attack action. Look at Fire Bolt, ranged spell attack, not an attack action. Look at BB and GFB, make a special melee attack as part of the casting, still not attack action. Look at Vampiric Touch, special melee spell attack as an action each round, not an attack action.

if eating a good berry is Use an Object, and throwing an Acid Vial is Use an Object, I’m inclined to think throwing a Magic Stone is as well. there may actually be an angle here to redeem this spell...

Quote from Chicken_Champ >>

Yes, that would be decent... I suppose you could travel with three hirelings (or Skeletons you’ve raised?) and essentially treat it like an off brand Eldritch Blast by having them use all three pebbles every round? That has potential...

Is the pebble attack a Special Action, or a Use an Object action, do you think? If it’s Use an Object, I suppose a Thief might be able to do it twice per round... and even a Familiar might be allowed to use it????

That's a good question, and I really don't know.  I would probably rule that it's a Special Action, but I can certainly see the case for it being the [Tooltip Not Found] action... Interesting.

Edit:  Been pondering it, and if a DM does rule that Familiars can throw them... imagine a Warlock with Flock of Familiars going, using his BA to give them Magic Stones to throw, and action using Eldritch Blast.  How glorious.

Generally, when a spell gives me the ability to later make an attack with an action, I'm quite content calling that an untyped Special Action. Vampiric Touch, Call Lightning, that sort of thing. But in Chapter 9: Combat, we are specifically provided a "Use an Object" action:

Use an Object

You normally interact with an object while doing something else, such as when you draw a sword as part of an attack. When an object requires your action for its use, you take the Use an Object action. This action is also useful when you want to interact with more than one object on your turn.

So let's look at Magic Stone:

You touch one to three pebbles and imbue them with magic. You or someone else can make a ranged spell attack with one of the pebbles by throwing it or hurling it with a sling. If thrown, it has a range of 60 feet. If someone else attacks with the pebble, that attacker adds your spellcasting ability modifier, not the attacker’s, to the attack roll. On a hit, the target takes bludgeoning damage equal to 1d6 + your spellcasting ability modifier. Hit or miss, the spell then ends on the stone.

The spell seems pretty clear that it isn't the spell that is providing a special action, but rather something that you or an ally can do "with one of the pebbles." I think it's pretty self evident that pebbles are objects... it really feels like we've satisfied the conditions to call this a Use an Object action instead of some other special untyped action.

But... I just remembered that the DMG changes this in Chapter 7: Treasure, providing that there's actually another type of action called "Activating an Item" which is distinct from Use an Object. 

Activating an Item

Activating some magic items requires a user to do something in particular, such as holding the item and uttering a command word, reading the item if it is a scroll, or drinking it if it is a potion. The description of each item category or individual item details how an item is activated. Certain items use one or more of the following rules related to their activation.

If an item requires an action to activate, that action isn't a function of the Use an Object action, so a feature such as the rogue's Fast Hands can't be used to activate the item.

Is a magically enhanced pebble an object, or a "magic item"? If it is a "magic item" and not just a (magical) object, is throwing it "activating" it, or just "using" it? Gray area abounds...

This distinction would not stop a Familiar from throwing the pebble either way, I think there's some good synergy there. But it would stop a thief with Fast Hands from throwing two pebbles, if throwing a Magic Stone is Activating an Item instead of Use an Object. 

HMMMMMM

Bonus Round: Does Flame Blade actually create an object (a flaming sword), or just a spell effect? If it's a Use an Object action to attack with the blade, not Activate an Item, have we found a way to redeem Flame Blade for thieves? 

HMMMMMM indeed, it's quite the interesting thought experiment.  You may have missed my edit to my last post ^

Warlock, Flock of Familiars, Magic Stone, Eldritch Blast, ???, Arcane machine gun.

Bonus Round: Does Flame Blade actually create an object (a flaming sword), or just a spell effect? If it's a Use an Object action to attack with the blade, not Activate an Item, have we found a way to redeem Flame Blade for thieves? 

Interesting, but Flame Blade does say "you can use your action."  I think in it's case, this means it just the typical "special action" as it does say it uses up your action, but doesn't specify an action type.  Magic Stone also doesn't say what kind of action is used to make the ranged spell attack, but it doesn't say "use your action," like Flame Blade does, so it's more up for interpretation.

im not sure that language defeats it being considered using the object instead of using the spell itself, though it might. mundane items have similar verbiage as Flame Blade, like acid (vial)::

As an action, you can splash the contents of this vial onto a creature within 5 feet of you or throw the vial up to 20 feet, shattering it on impact. In either case, make a ranged attack against a creature or object, treating the acid as an improvised weapon. On a hit, the target takes 2d6 acid damage.

Given all this discussion about what action it is to throw the stone, it gives the idea that using a sling to make the spell attack could allow for multi attack. Other than extending the range, there is now another bonus to using the sling option?

Using the Sling does not transform it into a weapon attack, nor into a use of the Attack Action, sadly. 

Quote from Chicken_Champ >>

im not sure that language defeats it being considered using the object instead of using the spell itself, though it might. mundane items have similar verbiage as Flame Blade, like acid (vial)::

As an action, you can splash the contents of this vial onto a creature within 5 feet of you or throw the vial up to 20 feet, shattering it on impact. In either case, make a ranged attack against a creature or object, treating the acid as an improvised weapon. On a hit, the target takes 2d6 acid damage.

That's true.  I dunno, dealer's choice.  Letting a Thief use it twice with Fast Hands would certainly be fun.

Quote from Chicken_Champ >>

Using the Sling does not transform it into a weapon attack, nor into a use of the Attack Action, sadly. 

 But can you multi attack with a ranged weapon?

“Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.” - straight from the feature in the class list.

“With this action, you make one melee or ranged attack.” - from the “Actions in Combat” section of the PHB for “Attack.” Note it doesn’t specify a weapon attack here either.

I recall a sage advice clarifying the sling and magic Stone combo is a “Ranged spell attack” made with a “Ranged weapon.”

But if we leave it there, you could assume you can multi attack with a cantrip. Im pretty sure that’s not a thing.. so does anyone know where the rules exclude spell attacks from extra attack?

Quote from Aerow >>

Quote from Chicken_Champ >>

Using the Sling does not transform it into a weapon attack, nor into a use of the Attack Action, sadly. 

 But can you multi attack with a ranged weapon?

“Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.” - straight from the feature in the class list.

“With this action, you make one melee or ranged attack.” - from the “Actions in Combat” section of the PHB for “Attack.” Note it doesn’t specify a weapon attack here either.

I recall a sage advice clarifying the sling and magic Stone combo is a “Ranged spell attack” made with a “Ranged weapon.”

But if we leave it there, you could assume you can multi attack with a cantrip. Im pretty sure that’s not a thing.. so does anyone know where the rules exclude spell attacks from extra attack?

 

 Okay so spells have a stated action as their cast time. You can’t use two actions in a multi attack. Which seems to support that a sling allows for multi attack as you’re no longer using an action to throw a stone. You’re using your action to make an attack with a ranged weapon, which can happen twice with multi attack.

I like it.

I... I don’t understand why I’m not finding a section that says it doesn’t work like that, that you can only take the Attack action with a weapon or unarmed strike. How... how is there no section that says that???? 

attack

Attack

The most common action to take in combat is the Attack action, whether you are swinging a sword, firing an arrow from a bow, or brawling with your fists.

Attack

The most common action to take in combat is the Attack action, whether you are swinging a sword, firing an arrow from a bow, or brawling with your fists.

With this action, you make one melee or ranged attack. See the "Making an Attack" section for the rules that govern attacks.

Certain features, such as the Extra Attack feature of the fighter, allow you to make more than one attack with this action.

Certain features, such as the Extra Attack feature of the fighter, allow you to make more than one attack with this action.

Yeah, I’m pretty sure that if a Druid hands 3 Magic Sones to a Fighter with a sling then the Fighter can launch them all in one turn if they have enough attacks.

What stops a fighter from using Vampiric Touch three times? Just the fact that it says, “as an action”?

Seems to be.