skill
spreadsheet-formatting-skill
Claude skill: format financial, marketing and operations tables in Google Sheets/Excel to ICAEW & FAST standards — colour encodes write permission, not decoration.
Set up
Skills are installed by placing their folder where your agent loads skills.
The download comes from github.com/haule2901/spreadsheet-formatting-skill itself, not from our server, so what you get is exactly what its author published.
Install instructions come from the README
README
synced Oct 23, 2026spreadsheet-formatting
A Claude skill that formats data tables in Google Sheets and Excel to international presentation standards — ICAEW's 20 Principles for Good Spreadsheet Practice, the FAST Standard, and the 60/30/10 colour rule.
It is not a theme. The core idea is that colour encodes write permission, not decoration: anyone opening the file should see at a glance which cells they may type into, which are calculated, and which are wrong.
Why this exists
Most "make my sheet look nice" attempts fail the same three ways:
- One standard applied to every table. A cash book, an ads report and a stock ledger need genuinely different treatment. Negative is bad in finance, impossible in inventory, and neither in marketing — CPA falling is good news.
- Colour used as decoration. If green just means "nice" and red just means "attention", the reader learns nothing and stops looking.
- Ratios averaged.
=AVERAGE(CTR)in a total row is the most common error in marketing spreadsheets, and formatting alone will never reveal it.
This skill forces a classification step first, then applies the standard for that specific table type — and reports the data errors it finds on the way through.
Install
Claude Code
git clone https://github.com/haule2901/spreadsheet-formatting-skill.git ~/.claude/skills/spreadsheet-formatting
Claude Desktop / any agent that reads SKILL.md — drop the folder wherever your skills live, keeping the directory name spreadsheet-formatting.
Then just ask, in plain language:
"Format this sheet properly: [paste your Google Sheet link]"
Works best with
Google Sheets access via the google-workspace MCP — cell-level read/write, formatting, conditional formats, charts. Without it the skill still applies to Excel through openpyxl / xlsxwriter, or as a written spec you follow by hand.
What it does
An 11-step sequence, run in order:
| Step | |
|---|---|
| 1 | Classify the table on two axes — data type (financial / marketing / operations) and sheet role (report / journal / derived / lookup / printable form) |
| 2 | Read the structure: header rows, section rows, subtotals, which columns are formulas |
| 3 | Clear stale conditional-format rules (the top cause of unpredictable colour) |
| 4 | Reset the range to neutral |
| 5 | Apply the header tiers |
| 6 | Apply number and date formats for the type identified in step 1 |
| 7 | Colour-code write permission — yellow = fill me in, grey italic = calculated |
| 8 | Add error warnings, only where something is actually wrong |
| 9 | Freeze panes, set column widths |
| 10 | Re-read and confirm the numbers still tie |
| 11 | Report the classification, and the data errors found while formatting |
Step 11 is usually worth more than the formatting. Walking every cell is the best chance you get to catch missing rows, totals that don't tie, blank parameters, and ratios computed the wrong way.
Reference material included
- Structural colour palette with exact RGB values
- Number-format strings per data type, including why financial zeros render as
–in a report but empty in a journal - Seven marketing-specific rules — attribution windows, retroactive revision, small-sample fading, why ratios can't be averaged
- Ready-made conditional-format formulas for common data errors
- How to build a cross-check block that actually proves something (both sides must be independent)
- Google Sheets API pitfalls:
TEXT_NOT_EQdoesn't exist,frozenColumnCountand merged cells, the 20KB payload ceiling,ARRAYFORMULAlimits
Standards referenced
- ICAEW — 20 Principles for Good Spreadsheet Practice (search the ICAEW Excel Community; the URL has moved more than once)
- The FAST Standard
License
MIT — see LICENSE.