xlsx
XLSX is Anthropic's proprietary agent skill for creating, editing and cleaning spreadsheets with live formulas checked for errors; its license limits it to Claude and Anthropic's own products.
Install XLSX
In Claude Code, add Anthropic's skills marketplace
/plugin marketplace add anthropics/skillsThen install the document-skills plugin, which holds the Word, PDF, PowerPoint and Excel skills
/plugin install document-skills@anthropic-agent-skillsIn Claude.ai, Anthropic says its example skills are already available on paid plans: switch them on under Customize > Skills.
Or paste this into your coding agent: Install the agent skill xlsx from github.com/anthropics/skills.
A skill can include scripts that run on your computer, so read its source first.
What XLSX does
The XLSX skill teaches Claude to work with spreadsheet files: .xlsx, .xlsm, .xltx, .csv and .tsv. It loads when a spreadsheet is the main input or output, such as adding columns or formulas, building a chart, cleaning messy data or converting between table formats. It does not load when the result is a Word document, an HTML report, a script or a Google Sheets integration.
With the XLSX skill, Claude writes formulas instead of pasting computed results, so the sheet updates when inputs change, and it documents every assumption and hardcoded number. A bundled script recalculates the workbook with LibreOffice and names the cells with errors, and Claude fixes them all before delivering. It keeps to functions LibreOffice can check, avoiding XLOOKUP and FILTER. When editing your file, it matches your conventions and leaves existing formulas alone. Financial models get standard colors and number formats.
XLSX is one of Anthropic's four document skills, next to Word, PDF and PowerPoint. Unlike most skills in Anthropic's repository it is not open source: the license allows use only within Anthropic's own services and forbids copying, changing or redistributing it. That is why this page lists only Anthropic's install routes.
When to use XLSX
- You need a financial model or budget that recalculates when you change the inputs.
- You have a messy CSV export with bad headers or broken rows and want a clean spreadsheet.
- You want to add formulas, columns or a chart to an existing Excel file without breaking what is there.
- You need to convert data between CSV, TSV and Excel formats.
When to pick something else
- You work in Codex, Cursor, Gemini CLI or another agent that is not Anthropic's: the xlsx license bars copying the skill there.
- You want a Word report or a Google Sheets integration: the skill says it does not load for those; Anthropic's DOCX skill covers Word.
Which agents XLSX works in
Anthropic documents XLSX for Claude Code, Claude.ai, Claude API.
XLSX license
XLSX is published under Proprietary: use only within Anthropic's services, no copying or redistribution. The LICENSE.txt in the xlsx folder (read 2026-10-01) puts use under your agreement with Anthropic and forbids extracting the files from Anthropic's services, keeping copies outside them, copying them, making derivative works and redistributing them. Anthropic's README calls its four document skills source-available, not open source. You may read the files on GitHub, but you may not copy them into Codex, Cursor or any other agent, or publish a changed version.
Questions people ask
Can I use Anthropic's xlsx skill in Codex, Cursor or ChatGPT?
No. Its LICENSE.txt (read 2026-10-01) forbids keeping copies outside Anthropic's services, copying and redistribution, so it is meant for Claude.ai, Claude Code through Anthropic's plugin, and the Claude API. The open skills CLI does list it, but installing it into another agent copies the files, which the license forbids.
Why does the xlsx skill avoid XLOOKUP?
It recalculates every workbook with LibreOffice to find formula errors, and in files it writes LibreOffice cannot evaluate XLOOKUP, XMATCH, SORT, FILTER, UNIQUE or SEQUENCE. So it uses INDEX and MATCH for lookups and sorts or filters in Python before writing cells.
Related skills for documents and office files
- Obsidian Markdown: obsidian-markdown is Steph Ango's agent skill for writing Obsidian Flavored Markdown: notes with properties, wikilinks, embeds, callouts and block references that render correctly in an Obsidian vault.
- PDF (OpenAI): pdf is OpenAI's open-source agent skill for making and reviewing PDF files: the agent builds them with Python libraries, renders each page to an image and checks the layout before delivering.
- DOCX: DOCX is Anthropic's proprietary agent skill for creating, reading and editing Word files, including tracked changes, comments and tables of contents; its license limits it to Claude and Anthropic's own products.
- PDF: PDF is Anthropic's proprietary agent skill for reading, creating and editing PDF files, from pulling out tables to filling forms and OCR; its license limits it to Claude and Anthropic's own products.
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