You have never used WebRTC. Research it — but not the API.
Answer it out loud before you open anything. The value of the flags below is in comparing them to what you actually said — including whether you asked who uses it before naming what you would build it with.
The situation behind the question
The chat app's product owner wants video calls. Nobody on the team has touched WebRTC. You are given a day to "look into it" and report back. The interviewer asks what your report will contain and what it will not.
What it is really testing
Whether the candidate researches an unknown technology by asking what problem it solves, what it guarantees, how it fails and what the smallest experiment is — rather than by reading the API reference end to end and producing a summary of it.