xlsx

xlsx is an open-source backend skill for Claude Code and compatible agents, published by anthropics. Its author describes it as: “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 column…”. The project has 170k stars on GitHub and ships custom license terms, so review them before reuse. Add it to your setup with `/plugin marketplace add anthropics/skills`.

What xlsx does

| 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** a model (formulas *and* values) | two `load_workbook` passes — see gotchas |

Installation

Add xlsx to your agent with:

/plugin marketplace add anthropics/skills

Always review a skill's source before installing it. This command comes from the skill's public repository; the linked repo is the source of truth for exact setup steps.

What's inside

The SKILL.md for xlsx is organised into these sections:

• Requirements for every output
• Recalculate (mandatory whenever the file contains formulas)
• Choosing formulas that survive verification
• openpyxl gotchas
• Financial models
• Dependencies

When to use it

Reach for xlsx when you want backend help from your agent without writing the same instructions every session. Load the skill and the agent picks it up automatically for relevant tasks.

Strengths

• Ships in anthropics/skills, an established project with 170,235 GitHub stars
• Actively maintained (recent commits)

Things to check

• No license declared — confirm terms with the author before reuse

Topics

Frequently asked questions

What does xlsx do?

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. Trigger especially when the user references a spreadsheet file by name or path — even casually (like "the xlsx in my downloads") — and wants something done to it or produced from it. Also trigger for cleaning or restructuring messy tabular data files (malformed rows, misplaced headers, junk data) into proper spreadsheets. The deliverable must be a spreadsheet file. Do NOT trigger when the primary deliverable is a Word document, HTML report, standalone Python script, database pipeline, or Google Sheets API integration, even if tabular data is involved.

How do I install xlsx?

Run /plugin marketplace add anthropics/skills in your agent, then reload your skills. Review the source at https://github.com/anthropics/skills before installing.

Is xlsx free to use?

xlsx is publicly available on GitHub, but anthropics has not declared a standard open-source license (Custom terms). Confirm the terms with the author before reusing it.

Where does xlsx come from?

xlsx ships inside anthropics/skills, a repository that contains 21 catalogued skills in total. The repository's 170,235 GitHub stars apply to that whole collection, not to this skill on its own.