Spreadsheets are the lingua franca of the data world — but getting AI to operate Excel correctly has always been tricky: formulas must recalculate, merged cells hide traps, and older runtimes choke on new functions. Anthropic's official XLSX Skill handles these details so Claude Code and compatible agents can work with spreadsheets like a data assistant.
What it covers: read/write, formulas, formatting, cleaning
Create & edit: build .xlsx workbooks from scratch, or open/fix existing .xlsx, .xlsm, .xltx, .csv, and .tsv files; add columns, compute, format, and chart
Formulas first: writes recalculable formulas (never hardcoded results), with a built-in recalc engine that validates every formula and ships zero-error files
Data cleaning: restructures messy tables (bad rows, misplaced headers, junk data) into proper spreadsheets
Format conversion: converts between Excel-family formats, with pandas for bulk data in/out
Financial models: supports professional models with assumption cells and cross-sheet references
Under the hood: openpyxl + pandas
The skill picks the right tool per task: formulas & formatting via openpyxl, bulk data via pandas (read_excel/to_excel), quick look via markitdown. Its real value is an "anti-footgun" engineering layer: after writing formulas it forces a LibreOffice recalc to validate them, refuses modern functions like XLOOKUP that break compatibility, writes only the top-left anchor of merged cells, and does a two-pass load to separate formulas from cached values.
Typical use cases
Financial reports: have AI turn raw transaction data into a report with auto-summing formulas
Data cleaning: clean dirty exported CSVs (misaligned, duplicated, messy) into analyzable tables
Batch conversion: convert legacy .xls or .tsv files into standard .xlsx in bulk
Model building: build financial models with assumption inputs and sensitivity analysis
How to use & download
Claude Code users: drop the skills/xlsx directory into your project's .claude/skills/ folder. Then describe the task naturally ("summarize this CSV by month into an Excel file") and the agent handles the rest. Full source: official GitHub repo.
Other agent users: follows the standard SKILL.md convention, compatible with any Agent Skills–supporting toolchain. Official docs: Anthropic Agent Skills documentation.
Related resources
Combine it with the rest of the document-processing quartet: PDF skill (pdf), Word skill (docx), and PowerPoint skill (pptx). To turn image tables into Excel, pair it with Photo to Excel or Excel AI.