xlsx

A guide for creating, editing, and analysing spreadsheet files such as Excel workbooks, CSV files, and TSV files. It covers formulas, formatting, data analysis, and charts or other visual summaries.

In plain words
What is it for?
Building spreadsheets, analysing tabular data, modifying Excel files, adding formulas and formatting, and creating visualizations.
Why use it?
It helps produce spreadsheets with working formulas and consistent formatting, while preserving the conventions of an existing template when one is being edited.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/feicoder/skill-factory/xlsx
Any agent
npx skills add FeiCoder/Skill-Factory --skill xlsx
Clone the repo
git clone --depth 1 https://github.com/FeiCoder/Skill-Factory

Made for: Claude Code, Codex.

Per session 96 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,667 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 83% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00096 $0.02667
Opus 5 $0.00048 $0.01333
Sonnet 5 $0.00019 $0.00533
Haiku 4.5 $0.00010 $0.00267

Measured 2d ago against content hash 020ccdb59322, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

xlsx scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (recalc.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

83% identical to xlsx — 37 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

book2skills/skills/document-skills/xlsx/SKILL.md · 289 lines

How it starts

The opening of the file, as written. The whole thing — 289 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Requirements for Outputs

All Excel files

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

Read the full file on GitHub · 289 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 289 lines · 96 tokens per session scan A 020ccdb59322

Subscribe to this mod's changes

xlsx is a skill published in the GitHub repository FeiCoder/Skill-Factory (10 stars, last pushed 6mo ago), licensed MIT. It adds 96 tokens to every session and 2,667 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 83% identical to xlsx, differing in 37 lines, and is treated as a copy.

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