How to use the xlsx Excel spreadsheet agent skill

What is an agent skill, and what does the xlsx skill make the agent do?

An agent skill is a folder that contains instructions (a SKILL.md file) and sometimes scripts that an AI agent reads when a task matches the skill's description. The xlsx skill is for creating and changing Excel workbooks.

Once installed, the agent can build a workbook with headers, rows and number formats, add live Excel formulas, style cells, add conditional formatting, dropdown lists (data validation), named ranges, frozen panes and merged cells, and create multiple sheets. It can also make surgical edits to a workbook you already have, matching its existing layout. The skill tells the agent to write real formulas rather than pasting computed numbers, so the sheet stays live when inputs change.

How do you install the xlsx skill?

Option 1: download the ZIP from the skill's page on this site and unzip it into your personal skills folder, ~/.claude/skills/, or into a project's .claude/skills/ folder.

Option 2: in the Claude apps, go to Settings, then Capabilities, then Skills, and upload the skill there.

The skill's files include SKILL.md. After unzipping, the skill folder should contain that file.

• Personal: ~/.claude/skills/
• Per project: .claude/skills/ inside the project folder
• Claude apps: Settings → Capabilities → Skills

What do you need before it works?

The skill needs Node.js with the bundled exceljs library, which the agent runs through brigade exec-node. LibreOffice (soffice) is optional and is used only for formula recalculation checks.

The skill runs scripts but does not use the network, according to its listing.

• Required: Node.js with the bundled exceljs library (via brigade exec-node)
• Optional: LibreOffice (soffice) for recalculation checks
• Runs scripts: yes. Uses network: no

How do you trigger the skill with a natural request?

The skill is meant to activate when you ask the agent to make, fill, update, model or edit a spreadsheet, workbook or .xlsx file. Describe the content and the structure you want. Name the sheets, columns, units and inputs where you can, because the agent follows any existing template you provide.

Example requests that match the skill's description:

• Make a 12-month sales tracker workbook with a Sales sheet and a Summary sheet, with totals as formulas.
• Build a simple three-year revenue model with a growth-rate input cell that the formulas reference.
• Add a dropdown with Low, Med and High to column A and turn negative values red in column B.
• Update the attached budget.xlsx: add a row for June and keep the existing formats.

What does the skill do behind the scenes?

For simple tables, the agent can use a make_document tool. For styling, validation, charts or models, it writes a small gen.cjs script using exceljs and runs it with brigade exec-node gen.cjs. For edits to an existing file, it uses an edit_document tool with set_cells and append_rows operations.

The skill sets two rules: formulas must be written as formula strings, not computed numbers, and numbers must be stored as numbers and formatted for display, not stored as text such as "$1.2M".

• Formulas are written as strings, for example =B5*(1+$B$6)
• Input cells are formatted in blue font, formulas in black, following a common banker convention
• Currency uses formats like $#,##0, percentages 0.0%

What should you check before you rely on the file?

exceljs stores formulas but does not calculate them. A broken reference such as #REF! or a division by zero (#DIV/0!) will not appear until the file is opened. If LibreOffice is installed, the skill can convert the file to PDF to look for error values. If it is not installed, the agent is told to check ranges by hand and keep formulas simple.

Open the file yourself and check totals, key formulas and sheet names before sharing it.

• Open the workbook in Excel and check key totals against your own calculation
• Look for any #REF!, #DIV/0! or similar errors
• Confirm sheet names and that existing sheets were not disturbed when editing