Question: One of my players and I differed on how we interpreted the [Chuul](https://www.dndbeyond.com/monsters/16824-chuul)'s multiattack the other night. Below is the MM text:

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> ***Multiattack.*** The chuul makes two pincer attacks. If the chuul is grappling a creature, the chuul can also use its tentacles once.
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If a Chuul grapples a creature as a result of its Multiattack, can it make a tentacle attack on the same turn?

The situation was as follows:

The chuul attacked player A with its first pincer attack and missed. It attacked A with its second pincer attack and hit, thus grappling A. I ruled that the tentacle attack could occur on the chuul's next turn if A were still grappled. (The other possible ruling is that the tentacle attack can occur on the chuul's current turn.)

My thinking is that a Multiattack is one action, and that the "If the chuul is grappling..." is a prerequisite condition to the action that must be met to grant the tentacle attack. The wording of "grappling", as opposed to "grapples", means that the chuul must be currently grappling the target before the Multiattack action is taken.

Which is the correct interpretation?

Answer: 
Questionable, but yes, it can.
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As far as I can tell there is not a rule or ruling that decides this situation in either direction. The answer depends on whether the creature needs to meet all conditions for the targets of the attack action when using Multiattack when declaring the action.

There is no ruling stating that all the conditions of the Multiattack have to be met at the start of the Attack action.

Since there are no rules declaring this specifically, I would apply a similar ruling for the Extra Attack feature. 

According to [a tweet by Jeremy Crawford](https://www.sageadvice.eu/2015/06/01/extra-attack-targets/) about Extra Attack, *you can pick your target before each attack*. If we suppose the same rule applies for Multiattack, then the creature can choose to use its tentacle attack because it has a valid target at that point and the condition is met.
Based on English grammar I would argue that it can't tentacle attack on this turn.
The form used in the sentence "if it is grappling a creature" is the present continuous. This form is used for two cases [(source)](https://learnenglish.britishcouncil.org/english-grammar-reference/present-continuous):

* **activities at the moment of speaking**. This means when declaring the attack action, something is already grappled. You also wouldn't say "I am attacking" if you are not right now doing it but declaring the intent to do so in the near future.
* **future plans or arrangements**. There is no arrangement to grappel someone. Also from my understanding this usage of present continuous would require specifying the time when you plan on doing it. "if at the end of the attacks it is grappling someone, it may use its tentacle as well".