xlsx

XLSX Skill

Create, read, and edit Excel workbooks — formulas, formatting, charts, data cleaning, and format conversion. Every formula-bearing output must be recalculated and error-free before delivery.

When to Use

Use this skill any time a spreadsheet file is the primary input or output: opening, reading, editing, or fixing an existing .xlsx, .xlsm, .xltx, .csv, or .tsv file; creating a new spreadsheet from scratch or from other data; converting between tabular formats; cleaning messy tabular data into a proper spreadsheet. Trigger whenever the user references a spreadsheet file by name or path — even casually. Do NOT trigger when the deliverable is a Word document (docx skill), HTML report, standalone script, or Google Sheets API integration. For finance-grade modeling conventions (DCF, LBO, three-statement), the optional excel-author skill adds stricter standards on top of this one.

Prerequisites

pip install openpyxl pandas "markitdown[xlsx]"
which soffice || sudo apt install -y libreoffice   # formula recalculation (scripts/recalc.py)

macOS: brew install libreoffice.

Quick Reference

Task	Approach
Create or edit with formulas/formatting	openpyxl — see gotchas below
Bulk data in or out	pandas (read_excel, to_excel)
Quick look at a sheet	markitdown file.xlsx — ## SheetName per sheet; reads .xlsm too. No cell coordinates, so don't plan edits from it. (read_file also auto-extracts .xlsx)
Read a model (formulas and values)	two load_workbook passes — see gotchas

Script paths below are relative to this skill's directory.

Requirements for every output

• Professional font (Arial, Times New Roman) throughout, unless the user says otherwise.
• Zero formula errors. Never ship while recalc.py reports errors_found. If you think an error predates you, prove it: load the original with data_only=True and look at that cell. An error you introduced looks exactly like one you inherited.
• Use formulas, never hardcoded results. Write sheet['B10'] = '=SUM(B2:B9)', not the Python-computed total. The sheet must recalculate when its inputs change.
• Follow the user's spec literally. Exact tab names, exact column headers, and the formula they spelled out. A redesign that computes something else fails, however elegant.
• Document every assumption and hardcoded number where the reader will see it — a cell comment, or an adjacent cell at a table's end. Cite a real source when one exists; when the number came from the user, say so plainly.
• A workbook you create for someone to fill in needs a short legend naming which cells to edit, and one example row of realistic values showing the expected format. Never add such a row to a file you were asked to edit.
• Editing an existing file: match its conventions exactly. They override every guideline here. Find its designated input cells first — a distinct font color, fill, or shading marks them — write only there, and leave every existing formula untouched.