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Author: Anthropic

Claude XLSX skill — Spreadsheets that keep formulas

Build and edit real .xlsx workbooks with formulas, charts, and formatting — not CSV dumps that break the model the finance team already uses.

Access: Claude paid tiers often ship spreadsheet document skills built-in (or via the document-skills plugin). The skill artifact on GitHub is free to browse/clone; host Claude product plans may still apply for runtime use.

What it does
Gives Claude spreadsheet-native steps: sheet layout → formulas that recalculate → charts/formatting → export that opens cleanly in Excel or Google Sheets.
Best for
Operators, analysts, and founders who need budgets, trackers, and model templates someone else will open in Excel tomorrow.
How to install / use
Enable Anthropic’s xlsx skill from anthropics/skills (or Claude document-skills plugin / built-in document skills on eligible paid plans). Define sheets, key formulas, and input cells before filling data.

If someone has to open it in Excel tomorrow, attach xlsx before you invent the grid.

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  • Separate inputs (blue) vs formulas (black) — never hard-code calculated cells
  • Name sheets by job: Inputs / Model / Charts — not Sheet1
  • Ask for a formula audit list: cell → formula → depends on

When to use

Use Anthropic’s official xlsx Agent Skill when the deliverable must remain an editable workbook — formulas that recalculate, multiple sheets, charts, and formatting — not a pasted markdown table someone retypes into Excel.

Good fits:

  • Budget / forecast models with input cells and dependent formulas.
  • Ops trackers (pipeline, inventory, hiring) that need filters and totals.
  • Chart-backed summaries for a board or weekly ops review.
  • Cleaning a messy export into a structured workbook with validation notes.

Avoid it when you only need a quick mental-math answer, a one-row Slack update, or a CSV for a script that will never be opened by a human in Excel.

Access note

Claude paid tiers often include spreadsheet document skills built-in, or via Anthropic’s document-skills plugin. The skill folder on GitHub is free to browse and clone. Baonat lists it for host-subscription users — we do not sell a separate paid skill pack. Runtime still depends on your Claude plan or API surface.

Why

Chat-native “spreadsheets” usually arrive as static numbers. Change one assumption and everything is wrong. Anthropic’s public xlsx skill (in anthropics/skills) keeps workbook structure first-class: create and edit .xlsx with real formulas, sheets, and charts instead of hoping paste survives.

Baonat marks this verified. Artifact on GitHub is free; Claude product billing may still apply when you run it.

Install

  1. Get the skill from skills/xlsx, or install Anthropic’s document-skills plugin / use Claude’s built-in document skills per Agent Skills overview.
  2. Specify workbook shape: sheet names, which cells are inputs, which are formulas, currency/date formats.
  3. Build skeleton first — headers + formulas with empty or sample inputs — then load real data.
  4. Request a formula audit (cell → formula → precedents) before you trust totals.
  5. Open in Excel/Sheets and change one input to confirm recalculation.
  6. Human review for finance-critical models.

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Kickoff prompt:

Attach the xlsx skill. Goal: [budget|tracker|model|clean-export].
Sheets: [Inputs / Model / Charts]. Inputs editable; calculated cells are formulas only — never hard-coded.
Formats: [currency/dates/%]. Sample or real data: [attach or paste].
First: sheet outline + key formulas. Then build the .xlsx.
Finish with a formula audit list and a one-row "how to use" note on Inputs.

Concrete scenarios

  1. Hiring plan. Headcount inputs drive salary, tax, and total burn formulas across months.
  2. Pipeline tracker. Stages, amounts, and weighted totals with a simple chart sheet.
  3. Export cleanup. Turn a messy CSV into typed columns, totals, and a validation sheet of odd rows.

Pitfalls / when NOT to use

  • Hard-coded “formulas.” If changing an input does nothing, reject the file.
  • One giant sheet. Split Inputs vs Model early.
  • Silent unit mismatches. State currency and percent scales in the prompt.

FAQ

Q: Official Anthropic skill?
A: Yes — xlsx under anthropics/skills, plus Claude Agent Skills docs.

Q: Google Sheets?
A: Same structure-first process; say the export target. Excel formulas usually translate; confirm after import.

Q: Free on GitHub?
A: The skill artifact is free to obtain. Paid Claude plans often already expose document skills at runtime.

Source attribution