Anthropic XLSX Skill
Skill
Official
Excel / XLSX
Open Source
Best for: Financial modeling, structured spreadsheet creation, and Excel automation with professional-grade formula integrity
Not ideal for: Quick one-off CSV reads — the financial modeling standards add overhead that's unnecessary for simple data tasks
What It Does
4
File formats (.xlsx .xlsm .csv .tsv)
0
Formula errors tolerated (#REF! #DIV/0!)
Official
Anthropic-maintained
Capabilities:
Read & analyze
Create workbooks
Edit & update
Format cells
Financial modeling
Formula recalculation
CSV / TSV import
Multi-sheet workbooks
Color-coded auditing
Core Features
🎨
Financial Modeling Color Standards
Enforces the professional color-coding convention used by investment banks and consulting firms. Blue = hardcoded inputs, Black = formulas, Green = cross-sheet references, Red = external links. Any output without correct color coding is considered incomplete.
✅
Zero Formula Error Principle
#REF!, #DIV/0!, #NAME?, and all other formula errors are treated as bugs, not acceptable output. The skill validates formula integrity before completing any task and iterates until all cells resolve cleanly.
🔄
LibreOffice Formula Recalculation
Uses soffice (LibreOffice) to trigger a full formula recalculation pass after edits, ensuring values shown in the file match what Excel or Google Sheets would compute. Catches circular references and volatile function issues that openpyxl cannot detect.
📐
Professional Number Formatting
Applies standard financial number formats automatically: currency with comma separators, percentage with 1–2 decimal places, EV/EBITDA multiples (1.0x format), and basis points. Numbers look right out of the box without manual formatting.
📂
Multi-Format Support
Reads and writes .xlsx, .xlsm (macro-enabled), .csv, and .tsv. For CSV/TSV, applies smart column type detection and can convert to a formatted .xlsx with headers, filters, and number formatting in one step.
Financial Modeling Color Code Reference
This skill enforces these conventions on every workbook it creates or edits:
| Cell Type |
Color |
Meaning |
| Blue font |
Hardcoded input |
Numbers you type directly — assumptions, growth rates, tax rates |
| Black font |
Formula |
Calculated cell — never hardcode, always trace to inputs |
| Green font |
Cross-sheet reference |
Formula that pulls from another sheet in the same workbook |
| Red font |
External link |
Formula that references another file — flagged for review |
Install
git clone https://github.com/anthropics/skills
cp -r skills/skills/xlsx ~/.claude/skills/anthropic-xlsx
pip install openpyxl
brew install --cask libreoffice
sudo apt-get install libreoffice
soffice --version
Note: LibreOffice (~600 MB) is required for the formula recalculation step. If you skip it, basic read/write/format tasks still work — only the recalc pass is unavailable.
Ratings
Financial Modeling Quality
4.7
Ease of use is 3.4/5 because LibreOffice install is required and the financial standards add setup steps. For users who don't need financial modeling, ease is higher.
Signals
Maintainer
Anthropic (official)
Dependencies
openpyxl + LibreOffice
Paired with
anthropic-pptx (same repo)