---
name: xlsx
description: "Create, edit, analyze, or convert Excel spreadsheets (.xlsx, .xlsm, .xltx) where the workbook file is the primary deliverable. Use for formulas, formatting, financial models, multi-sheet workbooks, and tabular cleanup exported to Excel. Also applies to .csv/.tsv when the user wants spreadsheet output. Do NOT use for Word documents, HTML reports, standalone Python scripts, database pipelines, or Google Sheets API work."
allowed-tools: Read Write Edit Bash Grep Glob
license: Proprietary. LICENSE.txt has complete terms
metadata:
  version: "2.1"
  skill-author: Anthropic, PBC
  adapted-by: K-Dense Inc.
  source: https://github.com/anthropics/skills/tree/main/skills/xlsx
compatibility: Requires Python 3.8+, LibreOffice (soffice on PATH), and gcc only when Unix sockets are restricted
---

# XLSX creation, editing, and analysis

| Task | Approach |
|---|---|
| **Create** or **edit** with formulas/formatting | `openpyxl` — see gotchas below |
| **Bulk data** in or out | `pandas` (`read_excel`, `to_excel`) |
| **Quick look** at a sheet | `markitdown file.xlsx` — `## SheetName` per sheet; reads `.xlsm` too. No cell coordinates, so don't plan edits from it |
| **Read** a model (formulas *and* values) | two `load_workbook` passes — see gotchas |

> `openpyxl`, `pandas`, and `markitdown` are preinstalled — do not run `pip install` first; write the script and import directly. Only if an import fails (or the `markitdown` command is missing): `pip install` the missing package.

> Script paths below are relative to this skill's directory.

## Requirements for every output

- **Professional font** (Arial, Times New Roman) throughout, unless the user says otherwise.
- **Zero formula errors.** Never ship while `recalc.py` reports `errors_found`. If you think an error predates you, prove it: load the *original* with `data_only=True` and look at that cell. An error you introduced looks exactly like one you inherited.
- **Use formulas, never hardcoded results.** Write `sheet['B10'] = '=SUM(B2:B9)'`, not the Python-computed total. The sheet must recalculate when its inputs change.
- **Follow the user's spec literally.** Exact tab names, exact column headers, and the formula they spelled out. A redesign that computes something else fails, however elegant.
- **Document every assumption and hardcoded number** where the reader will see it — a cell comment, or an adjacent cell at a table's end. Cite a real source when one exists (`Source: Company 10-K, FY2024, Page 45, Revenue Note, [SEC EDGAR URL]`); when the number came from the user, say so plainly.
- **A workbook *you create* for someone to fill in** needs a short legend naming which cells to edit, and one example row of realistic values showing the expected format. Never add such a row to a file you were asked to edit.
- **Editing an existing file: match its conventions exactly.** They override every guideline here. Find its designated input cells first — a distinct font color, fill, or shading marks them — write only there, and leave every existing formula untouched.

## Recalculate (mandatory whenever the file contains formulas)

openpyxl writes formulas as strings with **no cached values**. Until you recalculate, every
formula cell reads back as `None` to anything reading cached values — `pandas`,
`load_workbook(data_only=True)`, and most previewers.

```bash
python scripts/recalc.py output.xlsx [timeout_seconds]   # default 30
```

LibreOffice computes every formula, the file is **rewritten in place**, and you get JSON:
`status` (`success` | `errors_found`), `total_formulas`, `total_errors`, and an
`error_summary` naming up to 100 cells per error type (`locations_truncated` says how many it
withheld — trust `total_errors`, not the length of the list). Fix what it names and run it
again. **JSON with an `error` key instead of a `status` means nothing was recalculated**, and
only that case exits non-zero — `errors_found` exits 0, so never treat a clean exit as a clean
workbook.

**A green recalc proves your formulas *evaluate*, not that they are *right*.** An off-by-one
range or a reference to the wrong row yields a clean, error-free file with wrong numbers.
Write 2–3 formulas first and check they pull the values you expect, before building out a grid.

**A workbook that links to another file loses those links** if you re-save it with openpyxl and
then recalculate. Such a formula reads `='[1]Returns Analysis'!$B$2` — the `[1]` is an index
into the workbook's external-reference list, naming a *separate file on disk*, not a sheet.
That file is rarely present here, so the cell's cached value is the only thing holding its
data. openpyxl strips that value on save; LibreOffice then has to resolve the reference for
real, fails, writes `#NAME?`, and deletes every link. `recalc.py` refuses to run in that state
— copy those cells' values out of the original before you save over them (`--force` overrides,
and accepts the loss).

## Choosing formulas that survive verification

LibreOffice implements fewer functions than Excel, and one it cannot evaluate becomes a
literal `#NAME?` baked into the file you deliver.

- **Prefer Excel-2007-era functions** — `SUMIFS`, `INDEX`, `MATCH`, `IFERROR`, `SUMPRODUCT` — which need no prefix.
- **Six post-2007 functions work, but only with an `_xlfn.` prefix**, because openpyxl writes your formula into the XML verbatim and Excel stores post-2007 names prefixed (its UI hides the prefix): `_xlfn.TEXTJOIN`, `_xlfn.CONCAT`, `_xlfn.IFS`, `_xlfn.SWITCH`, `_xlfn.MAXIFS`, `_xlfn.MINIFS`. Written bare, each yields `#NAME?`.
- **Never use `XLOOKUP`, `XMATCH`, `SORT`, `FILTER`, `UNIQUE`, or `SEQUENCE`.** The runtime's LibreOffice cannot evaluate them under *any* prefix. Newer builds do evaluate them, but they are spilling array functions and an openpyxl-written file has no spill metadata, so only the top-left cell of the range gets a value — and `recalc.py` reports `total_errors: 0` on the truncated result. Use `INDEX`/`MATCH` for lookups, and sort, filter, and de-duplicate in Python before writing the cells.
- A formula LibreOffice could not parse is written back **lowercased** — a quick tell beside a `#NAME?`.

## openpyxl gotchas

- **Reading a model takes two loads.** `data_only=True` yields cached values with the formulas gone; the default yields formula strings with no values. One pass cannot give you both.
- **`data_only=True` is destructive if you save.** That workbook has no formulas left, so saving replaces every one with a literal — permanently.
- **`data_only=True` on a file openpyxl just wrote returns `None` everywhere** — run `recalc.py` first. (A formula whose result is `""` also reads back as `None`.)
- **Merged cells: write the top-left anchor only.** Every other cell in the range is a `MergedCell` whose `.value` is read-only.
- **`.xlsm` loses its macros unless you pass `keep_vba=True`** to `load_workbook`.
- **A sheet name containing a space must be quoted** in a cross-sheet reference: `='Assumptions Inputs'!$B$5`. Unquoted, it evaluates to `#VALUE!`.

## Financial models

Unless the user says otherwise, or the existing file already does something else.

**Color:** blue text (`0,0,255`) for hardcoded inputs and scenario levers · black for formulas ·
green (`0,128,0`) for links to another sheet · red (`255,0,0`) for links to another file ·
yellow fill (`255,255,0`) for key assumptions and cells the user should fill in.

**Numbers:** currency `$#,##0`, with the unit named in the header (`Revenue ($mm)`) · zeros
render as `-`, including in percentages (`$#,##0;($#,##0);-`) · negatives in parentheses ·
percentages `0.0%`, **stored as fractions** (`0.15` renders `15.0%`; storing `15` renders
`1500.0%`) · valuation multiples `0.0x` · years as text (`"2024"`, never `2,024`).

**Structure:** every assumption in its own labeled cell, referenced by the formulas that use it
(`=B5*(1+$B$6)`, never `=B5*1.05`) · formulas consistent across every projection period, since a
lone edited cell mid-row is the commonest silent error · guard denominators that can be zero.

## Dependencies

`openpyxl`, `pandas`, `markitdown` (pip, preinstalled — install only if an import fails or the command is missing) · LibreOffice (`soffice`, auto-configured for sandboxed environments via `scripts/office/soffice.py`)

---

*This skill is created and maintained by [Anthropic](https://github.com/anthropics/skills/tree/main/skills/xlsx). Vendored here unmodified except for frontmatter metadata; see LICENSE.txt for terms.*