XLSX
Data & Analyticsby anthropics
2/3 audits passSource-available (not open source)
Use this skill any time a spreadsheet file is the primary input or output. This means any task where the user wants to: open, read, edit, or fix an existing .xlsx, .xlsm, .xltx, .csv, or .tsv file (e.g., adding columns,…
XLSX teaches Claude to create, edit and analyse spreadsheet files (.xlsx, .xlsm, .csv, .tsv) with openpyxl for formulas and formatting, pandas for bulk data and markitdown for a quick read. Its rules for every output: use formulas rather than hardcoded results, ship zero formula errors, follow the user's spec literally, document every assumption and hardcoded number, and match an existing file's conventions exactly. Because openpyxl writes formulas without cached values, it makes recalculation mandatory through a bundled recalc.py script that runs LibreOffice and names each error cell, and it warns that a clean recalc proves formulas evaluate, not that they are right.
It also covers which functions survive verification (prefer SUMIFS and INDEX/MATCH; never XLOOKUP, FILTER or UNIQUE), openpyxl gotchas such as data_only=True destroying formulas on save, and financial-model conventions: blue inputs, black formulas, negatives in parentheses, percentages stored as fractions. Use it when the deliverable is a spreadsheet file. The skill says not to trigger when the output is a Word document, HTML report, standalone script, database pipeline or Google Sheets integration.
XLSX is published by anthropics under a proprietary, source-available licence. It is listed here for reference: it runs inside Claude's own apps and Claude Code, and it cannot be imported into BusinessMCP because its licence forbids copying.
What you can do with it
- Build a workbook where totals are live Excel formulas, not pasted values
- Clean a messy CSV export into a formatted spreadsheet
- Edit an existing model while keeping its input cells and formulas intact
- Lay out a financial model with standard input and formula colour coding
Run it on your business data
XLSX’s licence forbids copying, so it can’t be imported — install it in Claude directly.
Create your MCP endpointInstall it in a coding agent
One command adds XLSX to your project.
npx skills add https://github.com/anthropics/skills --skill xlsxHow we vetted it
- Source
- anthropics/skills at 3337550
- Licence
- Source-available (not open source)
- Security audits (skills.sh)
- Gen Agent Trust Hub: Pass · Socket: Warn · Snyk: Pass
- Bundled scripts
- Yes — read them before installing
Checked 2026-09-25 against its skills.sh listing. How we vet skills
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Frequently asked questions
Can I import XLSX into BusinessMCP?
No. XLSX is published by Anthropic under a proprietary, source-available licence that forbids copying, so it is listed for reference only. It runs inside Claude's own apps and Claude Code.
Why does the skill insist on recalculating the workbook?
openpyxl writes formulas as strings with no cached values, so anything reading values sees None until the file is recalculated. The skill runs its bundled recalc.py, which uses LibreOffice to compute every formula and report error cells.
How do I install XLSX?
Run `npx skills add anthropics/skills --skill xlsx` in a project that uses a skills-compatible agent such as Claude Code.