xlsx - SKILL.md Agent Skill

name: xlsx description: "Use this skill any time a spreadsheet file is the primary input or output. This means any task where the user wants to: open, read, edit, or fix an existing .xlsx, .xlsm, .csv, or .tsv file (e.g., adding columns, computing formulas, formatting, charting, cleaning messy data); create a new spreadsheet from scratch or from other data sources; or convert between tabular file formats. Trigger especially when the user references a spreadsheet file by name or path — even casually (like "the xlsx in my downloads") — and wants something done to it or produced from it. Also trigger for cleaning or restructuring messy tabular data files (malformed rows, misplaced headers, junk data) into proper spreadsheets. The deliverable must be a spreadsheet file. Do NOT trigger when the primary deliverable is a Word document, HTML report, standalone Python script, database pipeline, or Google Sheets API integration, even if tabular data is involved." license: Proprietary. LICENSE.txt has complete terms allowed-tools: [create_xlsx, read_xlsx, read_file, write_file]

Requirements for Outputs

All Excel files

Professional Font

Use a consistent, professional font (e.g., Arial, Times New Roman) for all deliverables unless otherwise instructed by the user

Zero Formula Errors

Every Excel model MUST be delivered with ZERO formula errors (#REF!, #DIV/0!, #VALUE!, #N/A, #NAME?)

Preserve Existing Templates (when updating templates)

Study and EXACTLY match existing format, style, and conventions when modifying files
Never impose standardized formatting on files with established patterns
Existing template conventions ALWAYS override these guidelines

Financial models

Color Coding Standards

Unless otherwise stated by the user or existing template

Industry-Standard Color Conventions

Blue text (RGB: 0,0,255): Hardcoded inputs, and numbers users will change for scenarios
Black text (RGB: 0,0,0): ALL formulas and calculations
Green text (RGB: 0,128,0): Links pulling from other worksheets within same workbook
Red text (RGB: 255,0,0): External links to other files
Yellow background (RGB: 255,255,0): Key assumptions needing attention or cells that need to be updated

Number Formatting Standards

Required Format Rules

Years: Format as text strings (e.g., "2024" not "2,024")
Currency: Use $#,##0 format; ALWAYS specify units in headers ("Revenue ($mm)")
Zeros: Use number formatting to make all zeros "-", including percentages (e.g., "$#,##0;($#,##0);-")
Percentages: Default to 0.0% format (one decimal)
Multiples: Format as 0.0x for valuation multiples (EV/EBITDA, P/E)
Negative numbers: Use parentheses (123) not minus -123

Formula Construction Rules

Assumptions Placement

Place ALL assumptions (growth rates, margins, multiples, etc.) in separate assumption cells
Use cell references instead of hardcoded values in formulas
Example: Use =B5*(1+$B$6) instead of =B5*1.05

Formula Error Prevention

Verify all cell references are correct
Check for off-by-one errors in ranges
Ensure consistent formulas across all projection periods
Test with edge cases (zero values, negative numbers)
Verify no unintended circular references

Documentation Requirements for Hardcodes

Comment or in cells beside (if end of table). Format: "Source: [System/Document], [Date], [Specific Reference], [URL if applicable]"
Examples:
- "Source: Company 10-K, FY2024, Page 45, Revenue Note, [SEC EDGAR URL]"
- "Source: Company 10-Q, Q2 2025, Exhibit 99.1, [SEC EDGAR URL]"
- "Source: Bloomberg Terminal, 8/15/2025, AAPL US Equity"
- "Source: FactSet, 8/20/2025, Consensus Estimates Screen"

XLSX creation, editing, and analysis

XLSX Creation

Use the create_xlsx tool. Provide the full workbook as a JSON spec.

Cell definition properties

value — string, number, or boolean
formula — Excel formula (e.g. "SUM(A1:A10)")
format — number format (e.g. "$#,##0", "0.0%", "#,##0;(#,##0);-")
bold, italic — boolean
bg_color — 6-digit hex string (no #) — fills cell background
fg_color — 6-digit hex string — sets font color
align — "left" | "center" | "right"
border — boolean — thin border all sides
colspan, rowspan — integer — merge cells

Color conventions (apply always unless template overrides)

Blue text "fg_color": "0000FF" — hardcoded inputs
Black text — formulas (default, no fg_color needed)
Green text "fg_color": "008000" — cross-sheet links
Red text "fg_color": "FF0000" — external file links
Yellow background "bg_color": "FFFF00" — assumptions cells

Example call

{
  "path": "model.xlsx",
  "sheets": [{
    "name": "Summary",
    "freeze_row": 1,
    "column_widths": [30, 15, 15, 15],
    "rows": [
      [{"value":"Item","bold":true,"bg_color":"4472C4","fg_color":"FFFFFF"},
       {"value":"FY2024","bold":true,"bg_color":"4472C4","fg_color":"FFFFFF"}],
      [{"value":"Revenue"},{"value":1000000,"format":"$#,##0"}],
      [{"value":"Growth","bold":true},{"formula":"(B3-B2)/B2","format":"0.0%"}]
    ]
  }]
}

XLSX Reading and Analysis

Use read_xlsx to read an existing file before editing.

{"path": "data.xlsx", "sheet": "Sheet1"}

Returns {"sheets": [...], "data": {"Sheet1": [[...], ...]}}.

Editing Existing Files

read_xlsx to understand current structure
Rebuild full workbook with create_xlsx incorporating the changes
Write to same path to overwrite

Validation Workflow

After create_xlsx:

Verify zero formula errors in all cells
Confirm column widths, freeze rows, number formats match spec
Spot-check formula cell values against expected results