Drill down on a cell in the Datarails Excel Add-in to see underlying detail — also the skill to use when the user asks to "explain the variance", "explain this number", "what's driving this", "what's behind this cell", or break a figure into its line items. In a live Excel context (add-in agent bridge available) DR formula cells drill through the add-in's own drill-down; with an .xlsx file (Claude Code) it resolves DR.GET formulas, reads hidden "dr control" filters, queries Datarails, and validates totals; with no workbook at all, the user can paste a DR.GET formula or give structured filters (no-file mode). Self-contained — discovers the client's financials table and fields on its own, no profile or setup step required.