claudegoodies
Skill

excel-author

From NousResearch

Build auditable Excel workbooks headless with openpyxl — blue/black/green cell conventions, formulas over hardcodes, named ranges, balance checks, sensitivity tables. Use for financial models, audit outputs, reconciliations.

Facts

Repository
NousResearch/hermes-agent
Status
Actively maintained
Last commit
Source file
optional-skills/finance/excel-author/SKILL.md

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The instructions Claude Code reads when this skill runs.

# excel-author

Produce an .xlsx file on disk using `openpyxl`. Follow the banker-grade conventions below so the model is auditable, flexible, and reviewable by someone other than the person who built it.

Adapted from Anthropic's `xlsx-author` and `audit-xls` skills in the [anthropics/financial-services](https://github.com/anthropics/financial-services) repo. The MCP / Office-JS / Cowork-specific branches of the originals are dropped — this skill assumes headless Python.

## Output contract

- Write to `./out/<name>.xlsx`. Create `./out/` if it does not exist.
- Return the relative path in your final message so downstream tools can pick it up.
- One logical model per file. Do not append to an existing workbook unless explicitly asked.

## Setup

```bash
pip install "openpyxl>=3.0"
```

## Core conventions (non-negotiable)

### Blue / black / green cell color
- **Blue** (`Font(color="0000FF")`) — hardcoded input a human entered. Revenue drivers, WACC inputs, terminal growth, market data.
- **Black** (default) — formula. Every derived cell is a live Excel formula.
- **Green** (`Font(color="006100")`) — link to another sheet or external file.

A reviewer can then scan the sheet and immediately see what's an assumption vs. what's computed.

### Formulas over hardcodes
Every calculation cell MUST be a formula string, never a number computed in Python and pasted as a value.

```pyth
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