What problem does it solve? Working with spreadsheet files programmatically often produces broken formulas, hardcoded values, and inconsistent formatting. This Skill provides a complete workflow for creating, editing, and analyzing .xlsx, .xlsm, .csv, and .tsv files while guaranteeing zero formula errors and professional financial-model formatting standards. ## Core Features & Use Cases - Formula-first spreadsheet generation: Builds Excel files with live formulas (SUM, AVERAGE, growth rates) instead of hardcoded Python-computed values, keeping workbooks dynamic and updateable. - Automated recalculation and error detection: The scripts/recalc.py tool uses LibreOffice to recalculate all formulas and reports #REF!, #DIV/0!, #VALUE!, #NAME?, and other errors with exact cell locations. - Financial modeling conventions: Enforces industry-standard color coding (blue inputs, black formulas, green cross-sheet links), number formatting (parenthesized negatives, 0.0% percentages, 0.0x multiples), and source documentation for hardcoded values. - Use Case: A user asks to build a revenue projection model from a messy CSV export. The Skill cleans the data with pandas, constructs the model in openpyxl with assumption cells and formulas, recalculates via LibreOffice, and fixes any reported errors before delivery. ## Quick Start Use the xlsx skill to create a financial model spreadsheet from my sales data CSV with formulas for totals and growth rates, then verify it has no formula errors.