From the request, it sounds like an attorney reached out by phone or letter and requested you provide a narrative in addition to the record previously provided. Based on the question, it does not sound like you received a valid subpoena. So, no, you do not have to comply, but, if you do, will you be saving yourself potential future required participation, such as deposition participation? It may be worth engaging directly, or having your attorney engage directly with the requesting lawyer to determine the impetus for the narrative request, and the resolve of the requesting lawyer for your further input. If the lawyer will not be satisfied without additional input, one way or another, you will likely be providing additional material.