Tex. Fam. Code § 301.106

A party's duty to amend and supplement written discovery regarding a testifying expert is governed by Rule 193.5, Texas Rules of Civil Procedure. If a party retains, employs, or otherwise controls an expert witness, the party must amend or supplement the expert's deposition testimony or written report only with regard to the expert's mental impressions or opinions and the basis for those impressions or opinions.