Comprehensive spreadsheet creation, editing, and analysis with support for formulas, formatting, data analysis, and visualization. When Claude needs to work with spreadsheets (.xlsx, .xlsm, .csv, .tsv, etc) for: (1) Creating new spreadsheets with formulas and formatting, (2) Reading or analyzing data, (3) Modify existing spreadsheets while preserving formulas, (4) Data analysis and visualization in spreadsheets, or (5) Recalculating formulas
SkillScore86Maintained
Automatic
◆Finance & Accounting pack
Last verified 8/12/2026
What it changes
Passed 17 of 20 test cases with the skill, and 12 of 20 without it.
Without skill59%
With skill86%
Checks it passed that the model alone missed
Specifies executing python3 recalc.py <excel_file> after saving formula modifications.
Specifies Red text (RGB: 255, 0, 0) for formulas containing external links to other files.
Advises keeping clean numbers in cells formatted with $#,##0 while explicitly stating units in column headers.
and 3 more in the full report
6 fixed13 passed either way3 still failing0 broke
Pass-rate lift
+27 pp
Tokens
+108%
Agent turns
0%
Response time
-21%
Model gemini-3.6-flashMeasured 8/12/2026v119 of 22 cases passed with skill · 20 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 6 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 6
Prompt
I am updating an established corporate financial model workbook that uses a custom green header fill and purple font for inputs. Should I reformat all inputs to industry-standard blue font (RGB: 0,0,255)?
What was checked, without and with the skill
Checked
Without skill
With skill
Instructs maintaining the existing template's visual design and conventions, as existing template patterns override general guidelines.
Missed
Passed
case-19 · gemini-3.6-flash · 8/12/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md283 linessingle file
Requirements for Outputs
All Excel files
Zero Formula Errors
Every Excel model MUST be delivered with ZERO formula errors (#REF!, #DIV/0!, #VALUE!, #N/A, #NAME?)
Comprehensive spreadsheet creation, editing, and analysis with support for formulas, formatting, data analysis, and visualization. When Claude needs to work with spreadsheets (.xlsx, .xlsm, .csv, .tsv, etc) for: (1) Creating new spreadsheets with formulas and formatting, (2) Reading or analyzing data, (3) Modify existing spreadsheets while preserving formulas, (4) Data analysis and visualization in spreadsheets, or (5) Recalculating formulas