What problem does it solve? Working with spreadsheet files programmatically often leads to broken formulas, hardcoded values that cannot update, and Excel errors like #REF! or #DIV/0! that go unnoticed until delivery. This Skill provides a structured workflow for creating, editing, and analyzing .xlsx, .xlsm, .csv, and .tsv files while guaranteeing zero formula errors in the final deliverable. ## Core Features & Use Cases - Formula-First Spreadsheet Creation: Builds Excel files using openpyxl with live formulas instead of hardcoded Python-computed values, so spreadsheets recalculate when source data changes. - Automated Formula Recalculation and Error Detection: Runs scripts/recalc.py with LibreOffice to recalculate all formulas and scan every cell for errors (#REF!, #DIV/0!, #VALUE!, #NAME?, #N/A), returning JSON with exact error locations. - Financial Modeling Standards: Enforces industry color conventions (blue inputs, black formulas, green cross-sheet links), number formatting rules, and assumption-cell placement for professional financial models. - Use Case: A user asks to build a revenue projection model from a messy CSV export. The Skill cleans the data with pandas, writes formulas with openpyxl, applies financial formatting, then recalculates and verifies the workbook contains zero errors before delivery. ## Quick Start Use the xlsx skill to create a formatted Excel financial model from my sales data CSV with live formulas and verify it has no formula errors.