Claude Excel skill (XLSX) review: verdict, safety and alternatives

Anthropic's XLSX skill teaches Claude to build and edit Excel workbooks with live formulas, then recalculate and error-check them. We rate it Recommended with caveats, 70/100, at Moderate confidence. A Windows crash in its recalculation script is the main caveat.

Get the skill: xlsx folder on GitHub · SKILL.md at the reviewed commit · skills.sh listing

Is there an Excel skill for Claude?

Yes, there is an official Excel skill for Claude, called xlsx, from Anthropic. It teaches Claude to build and edit workbooks with openpyxl and pandas. A bundled LibreOffice script recalculates and error-checks every formula before delivery.

An Agent Skill is a folder with a SKILL.md file that an agent loads when a task matches it. Our page with Agent Skills explained covers the format. The xlsx skill applies that format to spreadsheets. It triggers when a task involves an .xlsx file or a spreadsheet as the deliverable. The Help Center describes it in six words: "Enhanced Excel spreadsheet creation and manipulation".

The skill sits in the anthropics/skills repository next to 3 other document skills: DOCX, PDF and PPTX. Simon Willison found all four among Claude's built-in skills in /mnt/skills/public in October 2025. He noted they run on libraries that come preinstalled in Claude's containers.

The tools split into 3 jobs. The openpyxl library writes cells, formulas and formatting into .xlsx files. The pandas library reads and reshapes tabular data. LibreOffice runs headless through recalc.py, so every formula gets a computed value before Claude hands the file over.

Is the Claude Excel skill the same as Claude for Excel?

No, the Claude Excel skill is not the same as Claude for Excel. The skill builds .xlsx files inside code execution. Claude for Excel is an add-in that works inside the Excel app on your open workbook.

This page reviews only the skill. The add-in has no verdict on our site.

Is the Claude Excel skill worth installing?

Yes, the Claude Excel skill is worth installing in a Linux sandbox with LibreOffice. It scores 70/100, Recommended with caveats, at Moderate confidence. Tessl measured a 1.44x uplift, but recalculation crashes on Windows.

The skill is best for agents building or editing formula-driven workbooks and financial models. It runs best in a Linux sandbox with LibreOffice, such as Claude.ai code execution. It is a poor fit in 2 cases:

• Windows machines running Claude Code or the desktop Code tab, where recalc.py fails before LibreOffice starts.
• Chart- and drawing-heavy corporate templates that must open in desktop Excel without a repair dialog.

Its strength is short, specific rules. SKILL.md tells Claude to write formulas instead of hardcoded totals. It makes recalculation mandatory and lists the functions LibreOffice can evaluate. A guard refuses to wipe external links. Tessl measured a 1.44x uplift with Claude Sonnet 4.6, on two scenarios.

Its weakness is a set of reproduced defects with fixes left unmerged. The recalc.py script crashes on Windows. Claude Code argument substitution corrupts the $B$6-style examples. Prose containing #N/A fails the error gate. An openpyxl round-trip triggered Excel's repair dialog on a production template.

Our page on how we score a skill explains each measure below.

Cross-platform recalculation is the lowest score, at 30. Maintainability follows at 42. One substantive merge landed in July 2026. Over 15 xlsx fix or docs PRs opened after it, and none merged. The score sits at the bottom of the caveated band. See where it lands among Agent Skills ranked by verdict.

How many tokens does the Claude Excel skill use?

The Claude Excel skill loads 2,150 tokens per trigger, our measured file size per load. A 3-sheet budget model with about 200 formulas costs about 12,000 input and 4,000 output tokens, our estimate.

The hidden cost is time. Each recalc launches LibreOffice twice, once for the profile and once for the run. That takes tens of seconds per pass (estimate). Every fix-and-rerun loop repeats it. The script keeps its own output small: compact JSON, capped at 100 locations per error type.

Is the Claude Excel skill safe to install?

Yes, the Claude Excel skill is safe to install with care, at safety grade B. It makes no network calls and holds no secrets. Its helper can reuse a compiled shim from a fixed temp path on shared machines.

The skill ships instructions, one recalculation script and a shared office helper folder. Our review of the files at commit 8a1541c found 9 facts:

• Files: 53, and SKILL.md uses only recalc.py; the other helpers are shared office-folder code it never references.
• Macro: recalc.py writes a StarBasic macro into a per-run temporary LibreOffice profile.
• In-place rewrite: recalc.py rewrites the workbook in place, and SKILL.md discloses this.
• Shim: soffice.py builds an LD_PRELOAD socket shim in a fixed temp path, reusing any existing file (PR #1874).
• Network: only XML namespace URIs appear; there are no HTTP requests, hooks or MCP configs.
• Secrets: no environment-variable credentials and no telemetry.
• Link guard: recalc.py refuses to recalculate when external-link cells lost their cached values, unless --force is passed.
• Untrusted input: no guidance treats text or formulas inside input workbooks as untrusted.
• Audits on skills.sh: Gen Agent Trust Hub pass, Snyk pass, Socket warn without published detail.

The temp-path shim is the main deduction. A reviewer on PR #1874 planted a library at that path, and the helper loaded it. Run the skill in a sandbox or a single-user container. Keep a copy of the original workbook, because recalc.py rewrites it in place. Treat workbooks from outside your team as untrusted input. Our guide to vetting a skill's scripts shows the same review on any skill.

What does the community report about the Claude Excel skill?

The community reports a measured gain and several reproduced defects for the Claude Excel skill. Tessl measured a 1.44x uplift over two scenarios. GitHub issues document Windows crashes, corrupted formula examples and Excel repair dialogs.

These are the 14 dated reports we weighed. Two are positive, 1 is neutral and 11 are negative. Most negatives are GitHub issues and unmerged PRs that point at specific lines of code.

What are the Claude Excel skill's known failures?

The Claude Excel skill has four main known failures at commit 8a1541c. The recalc.py script crashes on Windows, and Claude Code corrupts $B$6-style examples. Prose with #N/A fails the error check, and round-trips can trigger Excel repair.

The worst failure is a workbook delivered as done that holds wrong, broken or hardcoded formulas. Lost external links and Excel's repair dialog count as the same failure. The four main failures, each still open on 2026-10-21:

• Windows crash: unguarded socket.AF_UNIX stops recalc.py on Windows, confirmed on 3 machines (issue #1120). Six fix PRs remain unmerged.
• Corrupted examples: Claude Code argument substitution rewrites $B$6-style references with argument words (issues #1779, #1462).
• False errors: any text cell containing #N/A fails the error gate (issue #1770).
• Repair dialog: Excel rejected a production template twice after an openpyxl round-trip (PR #1541).

Three smaller defects remain open:

• Header damage: filled title banners clip, and literal ampersands break headers (issue #1440).
• Link guard gap: the guard misses defined names written in a different letter case (issue #1464).
• Locale crash: soffice output with non-ASCII characters raises a UTF-8 decode error (PR #1854).

The Windows crash and the argument corruption hit local Claude Code setups. On Claude.ai, SKILL.md's Python packages come preinstalled. Each failure has the same remedy. Open the finished workbook in desktop Excel and check the totals before you send it.

Which agents and plans include the Claude Excel skill?

The Claude Excel skill is verified in Claude Code, and Anthropic ships it in Claude.ai and the API. Anthropic's sources disagree on plans. The Help Center says all plans, while the GitHub README says paid plans.

The two official sources conflict on plans. The Help Center skills article lists Free, Pro, Max, Team and Enterprise with no plan limit on Anthropic skills. The anthropics/skills README says the skills are "already available to paid plans in Claude.ai". We treat Free-plan access as unconfirmed until Anthropic aligns the two. Setup cost differs by surface too. Claude.ai needs zero setup, while local use needs LibreOffice and three Python packages.

The platform docs overview says the pre-built document skills are not built into Claude Code. The repository copy installs there through a plugin instead. Compare it with other top Claude Code skills on our ranked list.

How do you install the Claude Excel skill?

Install the Claude Excel skill in Claude Code through the document-skills plugin from the anthropics/skills marketplace. In Claude.ai, turn on code execution and the skill is ready. In the API, reference skill_id xlsx.

Each surface has its own route. Claude Code uses a plugin, Claude.ai uses a settings toggle and the API uses a container field.

In Claude Code

1. Add the marketplace: /plugin marketplace add anthropics/skills.
2. Install the bundle: /plugin install document-skills@anthropic-agent-skills.
3. Install LibreOffice and the Python packages openpyxl, pandas and markitdown.

The plugin installs docx, pdf, pptx and xlsx together. No requirements file ships with the skill, and PR #1571 to add one is unmerged. Windows users can install it, but recalc.py fails there (issue #1120). Claude Code can create Excel files, but its formula check fails on Windows. Our guide to installing skills in Claude Code covers plugin basics.

In Claude.ai

1. Open Settings > Capabilities.
2. Turn on Code execution and file creation.
3. Check Customize > Skills to confirm the skill is on.

Team and Enterprise admins manage skills under Organization settings > Plugins & skills. SKILL.md says openpyxl, pandas and markitdown come preinstalled, which holds for Claude.ai sandboxes. Our walkthrough on using skills in Claude.ai covers the same screens.

In the Claude API

1. Add a code execution tool to the request.
2. Set container.skills to the entry below.
3. Download the finished workbook through the Files API.

The API container has no network access and allows no runtime installs, per the platform overview.

How do you use the Claude Excel skill for models and formulas?

Use the Claude Excel skill by asking Claude for a model, a clean-up or edits to an existing workbook. It writes live formulas, runs recalc.py and reports errors. Open the result in desktop Excel before sharing.

The skill serves 5 tasks:

For a new model, describe the sheets, inputs and outputs you want. Claude writes formulas rather than computed numbers, runs recalc.py and fixes any error it reports. For an edit, attach the workbook. Claude loads it with openpyxl, changes the target cells and recalculates.

SKILL.md sets financial-model conventions for colour. Inputs are blue, formulas are black, cross-sheet links are green and external links are red. It bans 6 functions: XLOOKUP, XMATCH, SORT, FILTER, UNIQUE and SEQUENCE. LibreOffice cannot evaluate them, so recalc.py cannot check them. Ask for INDEX and MATCH when you need a lookup.

Test it yourself before you trust it with a client model:

• Edit a real chart-bearing template that holds a few formulas.
• Run recalc.py on the result.
• Open the file in desktop Excel.
• Check for a repair dialog and confirm the totals are correct.

A repair dialog confirms the round-trip defect from PR #1541.

What are the alternatives to the Claude Excel skill?

No reviewed alternative beats the Claude Excel skill for general workbooks. Unreviewed packs such as claude-office-skills and oria.one's banking models target narrower jobs. Anthropic's PDF and PPTX skills cover the other office formats.

Reviewed skills are ordered by verdict score. Only the XLSX skill handles workbooks, and unreviewed options carry no score:

The oria.one page sells its own 25-skill pack in 5 domains and never names Anthropic's skill. The claudecodehq.com post describes its own 4 spreadsheet skills, with no install steps. We rank only what we reviewed. For other office formats, read Anthropic's PDF skill review and Anthropic's PowerPoint skill review.

Where is the Claude Excel skill on GitHub?

The Claude Excel skill is on GitHub in the anthropics/skills repository at skills/xlsx. Our reviewed commit holds 53 files, but SKILL.md uses only recalc.py. GitHub code search finds 4,560 matching copies, forks included.

• Repository: anthropics/skills, 15 contributors.
• Reviewed commit: 8a1541c, dated 2026-09-28.
• Last skills/xlsx change: fa0fa64 on 2026-07-17, from PR #1447.
• Releases: none, and no version tags.
• Stars: 179,391 at review.
• Installs on skills.sh: 177.0K, from the skills.sh skill page on 2026-09-30.
• Exact copies in code search: 4,560, including the original and forks.

The mcpmarket.com listing is one such copy. It carries the same SKILL.md under another publisher's name, with 1 GitHub star. One directory page shows 3 contributors and Apache-2.0, and both figures are wrong. Download from the anthropics/skills source rather than a copy.

Common questions

Can Claude Code create Excel files?

Yes, with the xlsx skill installed through the document-skills plugin. Recalculation needs LibreOffice and fails on Windows.

Is there a skill for creating skills?

Yes, Anthropic publishes skill-creator in the same repository. Read the skill-creator verdict before you use it.

Is the Claude Excel skill free?

Yes, it costs nothing extra inside Claude, and its licence is source-available, not open source. The Help Center says all plans, while the README says paid plans.

Should I use an Excel MCP server instead?

The skill needs no server and no network access. We have not reviewed Excel MCP servers; see our page on skills versus MCP servers.

Does the Claude Excel skill work in Codex?

Unknown. We found no published run of it in Codex.