Xlsx

This is your go-to for anything where an Excel file is the final deliverable. It handles formula-heavy workbooks, financial models with proper color coding (blue for inputs, black for formulas, green for internal links), and all the formatting details that make spreadsheets actually usable. The skill enforces zero formula errors through a recalc pipeline using LibreOffice, and it's opinionated about things like making zeros display as dashes and formatting negatives with parentheses. Uses openpyxl for structure and pandas for data work. The key discipline here is writing Excel formulas instead of hardcoding Python calculations, so your spreadsheets stay dynamic. Not for reports or scripts, just spreadsheets that need to work.