How do I determine whether a descriptive response to a conversation with a vague subject should be masculine or feminine?

This is somewhat of a hard question to describe, so apologies if my phrasing is confusing. I’m basically asking how I should gender responses in which I refer to/describe larger conversations that have either multiple topics or a difficult to determine subject.

For example: let’s say someone texts me a link to a new research paper. I read it, think it’s interesting, and want to give a general reply along the lines of “C’est très interéssant(e) !“ Since what I’m referring to with “interéssant(e)” is somewhat vague, how do I determine whether my comment on it should be masculine/feminine?

In this example I feel like the subject could be many different things: “le document du recherche” (document being masculine) or “l’information” (information being feminine) to name a few. Do I need to pick a specific subject in order to talk about it, and is there a best practice for finding said subject when it is hard to determine? Would “intéressant” default to masculine here since the subject is a little fuzzy? If instead I were commenting on a conversation discussing multiple different unrelated points, would it be plural?

Thanks in advance!