Agent skill · writing content · bighardperson
Excel / XLSX
Create, inspect, and edit Microsoft Excel workbooks and XLSX files with reliable formulas, dates, types, formatting, recalculation, and template preservation. Use when (1) the task is about Excel, `.xlsx`, `.xlsm`, `.xls`, `.csv`, or `.tsv`; (2) formulas, formatting, workbook structure, or compatibility matter; (3) the file must stay reliable after edits.
Why this skill is useful
Provides specific guidelines for handling Excel files that the AI wouldn't reliably generate on its own, such as preserving workbook structure and managing date formats.
What it needs
About 4k tokens when loaded. Last updated 2026-04-26. 34 stars on the source repository.
What this skill does
When to Use Use when the main artifact is a Microsoft Excel workbook or spreadsheet file, especially when formulas, dates, formatting, merged cells, workbook structure, or cross-platform behavior matter. Core Rules 1. Choose the workflow by job, not by habit Use pandas for analysis, reshaping, and CSV-like tasks. Use openpyxl when formulas, styles, sheets, comments, merged cells, or workbook preservation matter. Treat CSV as plain data exchange, not as an Excel feature-complete format. Reading values, preserving a live workbook, and building a model from scratch are different spreadsheet jobs. 2. Dates are serial numbers with legacy quirks Excel stores dates as serial numbers, not real date objects. The 1900 date system includes the false leap-day bug, and some workbooks use the 1904 system. Time is fractional day data, so formatting and conversion both matter. Date correctness is not enough if the number format still displays the wrong thing to the user. 3. Keep calculations in Excel when the workbook should stay live Write formulas into cells instead of hardcoding derived results from Python. Use references to assumption cells instead of magic numbers inside formulas. Cached formula values can be stale, so do not trust them blindly after edits. Check copied formulas for wrong ranges, wrong sheets, and silent off-by-one drift before delivery. Absolute and relative references are part of the logic, so copied formulas can be wrong even when they still "work". Test new formulas on a few representative cells before filling them across a whole block. Verify denominators, named ranges, and precedent cells before shipping formulas that depend on them. A workbook should ship with zero formula errors, not with known #REF!, #DIV/0!, #VALUE!, #NAME?, or circular-reference fallout left for the user to fix. For model-style work, document non-obvious hardcodes, assumptions, or source inputs in comments or nearby notes. 4. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills bighardperson/excel-xlsx