We run an AI assistant over a construction company's SharePoint: 865 sites, about 400,000 documents. For a year it answered from PDF and Word only. This month we added Excel and PowerPoint. The extraction took an afternoon. The citation format took the real thinking, and that is what this post is about. The problem with "see Budget_2026.xlsx" An answer from a document assistant is only worth something if the reader can check it. For PDF that is easy: cite the page, the reader ope...