A set of rules for working with spreadsheet files such as Excel workbooks, CSV files, and TSV files.

Use it when reading, creating, editing, cleaning, formatting, or charting spreadsheet data.

It helps prevent common spreadsheet problems, including encoding mistakes and formula errors.

xlsx — Skill for Claude Code and Codex by unclutter-pro

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.

Any agent

npx skills add unclutter-pro/atlas --skill xlsx

Clone the repo

git clone --depth 1 https://github.com/unclutter-pro/atlas

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/unclutter-pro/atlas/xlsx.svg)](https://agentmods.dev/skills/unclutter-pro/atlas/xlsx)

Your own site

<a href="https://agentmods.dev/skills/unclutter-pro/atlas/xlsx"><img src="https://agentmods.dev/badge/skills/unclutter-pro/atlas/xlsx.svg" alt="Measured on agentmods" height="20"></a>

Per session 201 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 3,091 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin 88% 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.

Model	Per session	Once invoked
Fable 5.1	$0.00201	$0.03091
Opus 5	$0.00101	$0.01545
Sonnet 5	$0.00040	$0.00618
Haiku 4.5	$0.00020	$0.00309

Measured 7d ago against content hash af2fc84fe4a0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, 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 7d ago.

The scan reads SKILL.md. This mod also ships 13 executable files (scripts/office/helpers/__init__.py, scripts/office/helpers/merge_runs.py, scripts/office/helpers/simplify_redlines.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

88% identical to xlsx — 29 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.

app/defaults/skills/xlsx/SKILL.md · 303 lines

How it starts

The opening of the file, as written. The whole thing — 303 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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
Arial and Times New Roman both cover Latin-1 including German Umlauts (ÄÖÜäöüß) and common European diacritics. For CJK/Cyrillic/Greek deliverables switch to a font with the required script coverage.

Non-ASCII / Internationalization

.xlsx is UTF-8 internally — openpyxl writes Umlauts, accents, and CJK without extra setup. Pass strings as-is.
Reading source text: open(path, encoding="utf-8"). Default differs by platform; never rely on the implicit default.
CSV / TSV export: always set encoding="utf-8-sig". The BOM keeps Excel-on-Windows from misinterpreting UTF-8 as cp1252 (the classic Ã¤ for ä bug).
```
df.to_csv("out.csv", index=False, encoding="utf-8-sig")
# openpyxl-native write needs no encoding kwarg; the BOM trick is CSV-only.
```
Reading CSV produced by Excel: try encoding="utf-8-sig" first to strip the BOM, then fall back to cp1252 for legacy German exports.

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

Read the full file on GitHub · 303 lines

Files

What ships with it

53 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.

7d ago First seen · 303 lines · 201 tokens per session scan A af2fc84fe4a0

Subscribe to this mod's changes

xlsx is a skill published in the GitHub repository unclutter-pro/atlas (2 stars, last pushed 19d ago), licensed MIT. It adds 201 tokens to every session and 3,091 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 0 findings. It is 88% identical to xlsx, differing in 29 lines, and is treated as a copy.

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