Claude xlsx skill: create and edit Excel spreadsheets

The Claude xlsx skill’s SKILL.md description tells Claude to use it any time a spreadsheet file is the primary input or output: opening, editing or fixing .xlsx, .xlsm, .xltx, .csv and .tsv files, adding columns, formulas, formatting and charts, building a new spreadsheet from scratch or from other data, converting between tabular formats and cleaning messy tables. It is not meant for jobs where the deliverable is a Word document, HTML report, standalone script, database pipeline or Google Sheets API integration.

In the Claude apps it is one of the built-in document skills, listed as enhanced Excel spreadsheet creation and manipulation: with Code execution and file creation on, Claude uses it automatically when a request calls for a spreadsheet (Use skills in Claude). In the Claude API it is one of the pre-built Agent Skills for PowerPoint, Excel, Word and PDF, used with the code execution tool (Agent Skills overview). The skill’s instructions work with openpyxl for formulas and formatting and pandas for bulk data, ask for live formulas rather than hardcoded results, and require a recalculation pass with zero formula errors before a file is delivered. When editing an existing workbook, Claude is told to match its conventions and leave existing formulas untouched. Anthropic publishes the source as a reference under a proprietary license: source-available, not open source.