XLSX — Excel Workbook Creation, Editing & Analysis

What it does

This skill kicks in whenever the deliverable is a spreadsheet file (.xlsx, .xlsm, .xltx, or CSV/TSV destined for Excel). Claude writes formulas, formatting, and multi-sheet structures with openpyxl, moves bulk data with pandas, and previews existing sheets with markitdown.

The standout piece is verification. openpyxl writes formulas without cached values, so the bundled scripts/recalc.py runs the file through LibreOffice, rewrites it in place, and returns JSON with total_formulas, total_errors, and the exact cells that failed. The skill forbids shipping a workbook while errors_found is reported — and warns that a clean recalc proves formulas evaluate, not that they're correct.

It also encodes hard-won practical rules: which post-2007 functions need the _xlfn. prefix, which array functions (XLOOKUP, FILTER, UNIQUE, SORT, SEQUENCE) to avoid entirely, merged-cell write rules, keep_vba=True for macros, external-link data loss, and a full finance-model style guide (blue inputs, black formulas, $#,##0, percentages stored as fractions).

Who it's for

• Financial analysts building forecasts, DCFs, and budget models
• Accountants and planners who need live formulas instead of hardcoded numbers
• Data folks turning raw CSVs into polished, shareable Excel deliverables
• Anyone tired of AI-generated spreadsheets full of #NAME? cells

Examples

1. Build a model: "Create a 5-year revenue forecast with growth rates in dedicated assumption cells." → Blue input cells, black formula cells, $#,##0 currency formats, verified by recalc.
2. Edit an existing file: "Update only the yellow input cells in this budget workbook." → Existing formulas and conventions are preserved untouched.
3. Clean and export: "Merge these three CSVs into a multi-sheet workbook and add SUMIFS totals at the bottom of each sheet."

Install the skill I found on Claude Skill Mart.
Copy the skills/xlsx folder from the GitHub repo K-Dense-AI/scientific-agent-skills into my ~/.claude/skills/k-dense-ai-xlsx/.
When it's done, tell me in one line what this skill can do.