Institutional investor adds talent acq to upcoming call. What do you do?

As the famous Glengarry Glen Ross quote goes: "You never open your mouth until you know what the shot is".

I'd say take the call. If they sollicited you, listen to their offer. If you sollicited them, do your pitch. Acknowledge and clarify that you understand their position; communicate yours. Courtesy doesn't hurt.

I'd focus your pitch on what you need and want. You may think you don't want something but quite often it's just because you don't know much, and vice versa. That is unless you know exactly what you want and what you don't, but that certitude is too common to mean anything except for those who toute it as one of the important traits of great founders in a continual pattern recognition that glosses over serveral biases (survivor, selection, salience).

Talk to them and see what they want? Make a decision about what to do after you know what you have to decide about?

What kind of answers are you expecting?

Don't assume anything. Go on the call and hear them out. If they are looking to acqui-hire, say No. But don't assume anything.