#What it does

The XLSX skill handles all spreadsheet operations -- creating, reading, editing, and manipulating Excel files. It enforces professional standards including formula-based calculations (never hardcoded values), industry-standard color coding for financial models, proper number formatting, and mandatory formula verification.

#How to use

Activate when any spreadsheet file is the primary input or output, including .xlsx, .xlsm, .csv, or .tsv files.

Create a financial model for our revenue projections

Clean up this messy CSV and output a formatted Excel file

#Skill instructions

#Critical Rule: Formulas Over Hardcoded Values

Always use Excel formulas instead of calculating in Python and hardcoding results. The spreadsheet must remain dynamic and updateable when source data changes.

#Financial Model Standards

Color coding:

• Blue text: Hardcoded inputs and scenario values
• Black text: All formulas and calculations
• Green text: Links from other worksheets
• Red text: External links to other files
• Yellow background: Key assumptions needing attention

Number formatting:

• Currency: $#,##0 with units in headers
• Zeros displayed as "-"
• Percentages: 0.0% (one decimal)
• Multiples: 0.0x for valuation
• Negative numbers: Parentheses, not minus signs

#Library Selection

• pandas: Data analysis, bulk operations, simple data export
• openpyxl: Complex formatting, formulas, Excel-specific features

#Mandatory Workflow

1. Choose tool (pandas or openpyxl)
2. Create or load workbook
3. Add data, formulas, and formatting
4. Save to file
5. Recalculate formulas using scripts/recalc.py (mandatory if using formulas)
6. Verify and fix errors: Check for #REF!, #DIV/0!, #VALUE!, #NAME?

#Formula Verification Checklist

• Test 2-3 sample references before building the full model
• Confirm column mapping (Excel columns are 1-indexed)
• Check for NaN handling, division by zero, and cross-sheet references
• Start small, verify dependencies, test edge cases

This skill is from the Anthropic Skills Repository.