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The Claude Excel skill (xlsx): what it does and how to install it

The Claude Excel skill builds and edits .xlsx files with live formulas and checks them for errors. What's in it, how to install it, and its license limits.

By the Kipt team · Updated 23 October 2026

Source: anthropics/skills · Maintainer: Anthropic · License: Proprietary (source-available) · Checked: 23 October 2026

What is the Claude Excel skill?

The Claude Excel skill, named xlsx, is Anthropic's Agent Skill for spreadsheet files: it lets Claude open, fix, build and convert .xlsx, .xlsm, .csv and .tsv files, with working formulas and a recalculation check before delivery. It is for anyone who wants a spreadsheet they can open in Excel and keep using, not a table in chat.

It is one of the four document skills the repo README says power Claude's document capabilities, with pdf, docx and pptx. Its SKILL.md description begins: "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, computing formulas, formatting, charting, cleaning messy data); create a new spreadsheet from scratch or from other data sources; or convert between tabular file formats."

It goes on to say Claude should trigger it even for casual references to a spreadsheet by name, and for cleaning messy tabular data. It should not trigger when the main deliverable is a Word document, HTML report, standalone Python script, database pipeline or Google Sheets integration.

What does the Excel skill do?

The SKILL.md chooses tools by task: openpyxl to create or edit with formulas and formatting, pandas for bulk data in and out, markitdown for a quick look at a sheet, and two openpyxl loads to read a model's formulas and values together.

Its "requirements for every output" read like a reviewer's checklist:

  • A professional font such as Arial or Times New Roman, unless you say otherwise.
  • Zero formula errors.
  • Formulas, never hardcoded results: =SUM(B2:B9), not the total computed in Python.
  • Follow your spec literally: exact tab names, column headers and formulas.
  • Document every assumption and hardcoded number, with a real source where one exists.
  • When editing your file, match its existing conventions and leave existing formulas alone.

Recalculation is mandatory. Because openpyxl writes formulas without cached values, Claude runs scripts/recalc.py, which uses LibreOffice to compute every formula and returns JSON with the total formulas, total errors and the cells that failed. The skill warns that a clean recalculation proves formulas evaluate, "not that they are right," so Claude should test two or three formulas before building out a whole grid.

Formula choices. It prefers Excel 2007-era functions such as SUMIFS, INDEX, MATCH and IFERROR, requires an _xlfn. prefix for six newer ones like TEXTJOIN and IFS, and bans dynamic array functions like XLOOKUP and FILTER.

Financial models. Unless told otherwise, it uses a fixed color code (blue hardcoded inputs, black formulas, green links to other sheets), negatives in parentheses, percentages stored as fractions, years as text, and every assumption in its own labeled cell.

What's in the folder:

  • SKILL.md: the instructions above.
  • scripts/recalc.py: recalculates a workbook in place and reports errors.
  • scripts/office/: soffice.py (a LibreOffice wrapper), validate.py, validators and Office XML schemas shared with the other document skills.

How do you install the Excel skill?

Choose one route.

In the Claude app. Anthropic's Use skills in Claude article lists "Enhanced Excel spreadsheet creation and manipulation" among the built-in skills, on Free, Pro, Max, Team and Enterprise plans. Turn on Code execution and file creation in Settings, Capabilities; skills are toggled in Customize, Skills.

In Claude Code, signed in with claude.ai. The Claude Code skills docs say "some of Anthropic's skills, such as pdf and xlsx, always sync" into ~/.claude/skills/synced/ when you sign in with a claude.ai account (v2.1.273 or later). Run /skills to see it under claude.ai sync. Sessions using an API key or Amazon Bedrock don't sync. Anthropic's Agent Skills overview still says the pre-built document skills are not available in Claude Code, so if xlsx doesn't appear, use the plugin route below.

As a Claude Code plugin. The README's commands, in a session:

/plugin marketplace add anthropics/skills
/plugin install document-skills@anthropic-agent-skills

This installs xlsx with docx, pptx and pdf. Call it directly with /document-skills:xlsx.

With the skills CLI. From its skills.sh page:

npx skills add https://github.com/anthropics/skills --skill xlsx

Add -a claude-code for Claude Code. The folder lands in .claude/skills/xlsx/ in your project, or ~/.claude/skills/xlsx/ with -g. Codex and Cursor read the same SKILL.md format (Codex skills, Cursor skills); read the license notes below first.

Through the API. Reference skill_id xlsx with the code execution tool, per the Agent Skills overview.

How do you use the Excel skill?

Mention the file or the spreadsheet you want. Requests like these fit:

  • "Clean up the xlsx in my downloads: fix the misplaced headers and remove the junk rows."
  • "Build a 5-year revenue model with inputs on an Assumptions tab and formulas everywhere else."
  • "Add a column to sales.xlsx that shows each rep's share of the regional total."
  • "Convert these three CSV files into one workbook with a tab each and a summary sheet."
  • "Find out why the totals on the Q3 tab show #REF! and fix them without changing my layout."

Requirements on your machine. The SKILL.md lists openpyxl, pandas and markitdown from pip, treated as preinstalled and installed only if an import fails, plus LibreOffice for recalculation. Without LibreOffice, Claude can still write the file, but it can't run the error check.

Tips and limits

  • License. Like the other document skills, xlsx is "source-available, not open source," per the README. Its LICENSE.txt puts use under your agreement with Anthropic and forbids copying, keeping copies outside Anthropic's services, derivative works and redistribution. For your own conventions, write a separate skill.
  • Macros. The skill notes that .xlsm files lose their macros unless loaded with keep_vba=True, so mention macros if your file has them.
  • External links. Workbooks that link to other files lose those links when re-saved with openpyxl and recalculated; recalc.py refuses to run in that state unless forced.
  • Clean is not correct. An off-by-one range produces a file with no errors and wrong numbers. Spot-check key totals yourself.
  • Scripts run locally. In Claude Code, scripts execute on your computer. Anthropic's overview advises installing skills only from trusted sources and reviewing what they run.
  • Repo copy versus the app. The README warns Claude's built-in behavior "may differ from what is shown in these skills."

Save it in your Kipt library

The license doesn't allow copying these files, so don't import the xlsx folder into a library. Use Kipt for your own side of the work: spreadsheet prompts with {{variables}} for file names and periods, and your own skills, such as your team's model conventions, drafted with the free SKILL.md generator. Kipt keeps them as Markdown in your own private GitHub repo, and one command installs every skill into Claude Code or Codex:

npx skills add https://github.com/<you>/<repo>.git --all -g

Similar skills

Questions

What is the Claude Excel skill?

It is Anthropic's xlsx Agent Skill, which teaches Claude to create, edit and analyze spreadsheet files such as .xlsx, .xlsm, .csv and .tsv. It insists on real formulas instead of pasted results and recalculates every workbook to catch formula errors before handing it over.

Does the Excel skill write formulas or just values?

Formulas. The SKILL.md says to use formulas, never hardcoded results, so the sheet still recalculates when its inputs change. It then runs a LibreOffice recalculation script that reports any formula errors.

How do I get the Excel skill in Claude Code?

If you sign in to Claude Code with a claude.ai account, the docs say Anthropic's xlsx skill always syncs. You can also install the document-skills plugin from the anthropics/skills marketplace, or run npx skills add https://github.com/anthropics/skills --skill xlsx.

Can the Excel skill use XLOOKUP?

The skill tells Claude never to use XLOOKUP, XMATCH, SORT, FILTER, UNIQUE or SEQUENCE, because its LibreOffice check can't evaluate them reliably. It uses INDEX and MATCH for lookups and does sorting and filtering in Python before writing cells.

Does it work with Google Sheets?

Not directly. The description says not to trigger it when the deliverable is a Google Sheets API integration, a Word document, an HTML report, a standalone script or a database pipeline. The output must be a spreadsheet file.

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