document-xlsx

Document XLSX Skill - Quick Reference

Boundary: when the official Anthropic xlsx skill is available, prefer it for plain create/edit, formula-first financial models, LibreOffice recalculation (recalc.py) and formula-error scans. Use this skill for its specialist lanes:

• native charts, pivots, data validation and conditional formatting
• Office Scripts, Microsoft Graph and xlwings automation
• very large (write_only/read_only) files
• untrusted-workbook audit and sanitising

Core Decision Rules

• Decide the runtime first: local file generation, cloud workbook automation (Microsoft 365), desktop Excel automation, or audit and sanitising.
• XlsxWriter is write-only. It cannot open or edit an existing .xlsx. For "edit this workbook", use openpyxl (or ExcelJS in Node). Picking XlsxWriter for an edit task fails immediately.
• Table-first exports: headers in one row, a named Excel Table, a frozen header row and bounded ranges. The table brings its own autofilter, so a separate autofilter() over the same range raises OverlappingRange.
• Libraries write formulas; a calculation engine computes them. openpyxl does not evaluate formulas; XlsxWriter normally writes a placeholder cached 0 and requests recalculation, or accepts an explicitly supplied result. A nonblank cache is not calculation evidence. Keep formulas, recalculate in the target engine, and independently compute any result needed before that step. See XlsxWriter formula results.
• Future functions need their specified OOXML spelling. With openpyxl, check the function's required prefix in the writer's future-function list; openpyxl.utils.FORMULAE is not a compatibility test. Default to XlsxWriter write_dynamic_array_formula for spill formulas. If the recipient's Excel build is unknown, prefer INDEX/MATCH and nested IF. Load references/excel-formulas.md when writing future or array functions or reading cached results.
• Library defaults fail open. Set them explicitly:
  • Set validation error alerts and errorStyle="stop" explicitly for Excel entry checks; openpyxl itself never validates assigned values. Check inputs in code too.
  • XlsxWriter turns strings that start with = into formulas unless strings_to_formulas is off.
  • XlsxWriter add_table warns and returns a negative code instead of raising.
• Native pivots: use Office Scripts (Microsoft 365) or xlwings (desktop Excel). openpyxl and XlsxWriter cannot create them. For headless exports, write pre-computed summary tables.
• Untrusted workbooks: load with keep_links=False and keep_vba=False, and run scripts/xlsx_audit.py before anything else. This skill never authors or executes macros.
• Large files: install lxml and use Workbook(write_only=True) / load_workbook(read_only=True). Both stream instead of building the full tree. A write-only workbook can be saved exactly once (WorkbookAlreadySaved).
• Format ceilings: 1,048,576 rows × 16,384 columns per sheet, set by the file format. Decide pagination or a multi-sheet layout up front.