PowerBI-Claude-Design

A library of Claude.ai skill packages for authoring Power BI semantic models and reports — TMDL syntax, DAX measures, calculation groups, DAX UDFs, and a visual design system — plus a Contoso sample dataset and a working PBIP test project for trying everything out.

Every skill outputs plain text TMDL/DAX ready to paste into Power BI Desktop, Tabular Editor, or any TMDL-aware tool. No build step, no MCP required.

---

What's in here

PowerBI-Claude-Design/
├── tmdl-standards/         ← TMDL syntax foundation (start here)
├── measures/               ← DAX measure patterns & naming
├── calc-groups/            ← Calculation groups in TMDL
├── dax-udf/                ← DAX User-Defined Functions
├── design-system/          ← Visual design system (3-30-300, themes, KPIs)
│   ├── references/         ← colors / typography / layouts / components
│   ├── iconography/        ← Fluent line icons + status dots (21 SVGs)
│   └── wordmark/           ← Brand wordmark light/dark variants
├── power-bi-test/          ← Working PBIP project (Contoso) for testing skill output
└── datamodel/              ← Contoso sample dataset
    ├── ContosoDatacsv-10k.7z
    ├── ContosoDatacsv-10k/ ← 8 unpacked CSVs (~26 MB)
    └── contosoERD.png      ← Entity-relationship diagram

---

Skill packages

Each folder is a self-contained Claude skill — drop the SKILL.md (and any references/ / examples/) into a Claude.ai Project as knowledge files, then prompt naturally.

tmdl-standards/ — Foundation

Core TMDL ground rules that every other skill builds on:

• TAB-only indentation (mixed tabs/spaces = parse error)
• createOrReplace deployment wrapper
• Object declaration vs property syntax (name = expr vs prop: value)
• Quoting names with spaces, multi-line expression indentation
• What not to emit (expression: keyword on measures, lineageTag, formatStringDefinition)

Always start here. Everything below assumes these rules are in effect.

measures/ — DAX Measures

Production-quality DAX measure patterns:

• Naming prefixes (# count, $ currency, % ratio, Δ variance, Δ% percent variance)
• Display-folder taxonomy (Key Metrics, Time Intelligence, Budget vs Actual, …)
• Patterns: simple sum, SUMX row-level, conditional CALCULATE+FILTER, distinct count, DIVIDE rates
• Time intelligence: YTD / QTD / MTD / PY / PY YTD / Rolling N months
• KPI variance, status flags, semi-additive (LASTNONBLANK / LASTDATE)
• Error handling with DIVIDE / IFERROR / VAR + ISBLANK
• formatString quick reference

calc-groups/ — Calculation Groups

Replace banks of repeated time-intelligence or scenario measures with a single calc group:

• TMDL nesting rules (calculationItem at 3 TABs, body at 5 TABs, properties at 4 TABs)
• Time Intelligence group (None / Current / YTD / QTD / MTD / PY / PY YTD / vs PY / vs PY % / Rolling 3M / Rolling 12M)
• Scenario group (Actual / Budget / Forecast / vs Budget / vs Budget %)
• Currency conversion group (USD / EUR / GBP / JPY)
• Precedence ordering (higher number = outermost wrapper)
• ISSELECTEDMEASURE for excluding specific measures

dax-udf/ — DAX User-Defined Functions

Reusable typed functions stored in the semantic model:

• Type system: Scalar Int64/Decimal/Double/String/DateTime/Boolean/Numeric/Variant, Table, AnyRef
• Parameter modes:
  • Val (default) — argument evaluated at call site, value substituted
  • Expr — raw expression substituted, evaluated in inner context (for CALCULATE, FILTER, time intelligence)
  • AnyRef — pass column/table/measure references unevaluated (for VALUES, SAMEPERIODLASTYEAR, TREATAS)
• Worked examples: CircleArea, Mode, PriorYearValue, TodayAsDate, SplitString

design-system/ — Visual Design System

Standards and patterns for building professional, accessible reports — the visual layer that wraps everything the other skills produce. Adapts Microsoft Fluent principles for analytics:

• Core principles — consistency, accessibility (WCAG AA / 7:1 contrast, colorblind-safe palette), hierarchy, "answer specific questions"
• 3-30-300 Rule + detail-gradient layout (KPIs → Charts → Tables, top-left → bottom-right)
• KPI design — every KPI must answer "is this good or bad?" and "is it getting better or worse?" (target + gap, trend indicator, the "20% change test")
• Theme JSON — wildcards before per-visual overrides, ThemeDataColor over hardcoded hex, semantic color usage
• "Subtract, don't add" table design — remove gridlines / banding / decoration, sort by most important measure
• Anti-patterns — "Power BI Slop", bare KPI numbers, color overload, inconsistent spacing, missing alt text, slicer overload
• Checklists — accessibility audit + report evaluation rubric (12 items)
• references/ — colors.md (palette + theme JSON), typography.md (Segoe UI scale + Format pane mappings), layouts.md (canvas dims, grid, 5 templates), components.md (KPI cards, slicers, matrices, headers, tooltips)

design-system/iconography/ — Fluent Line Icons

20px viewBox, 1.5px stroke, currentColor so icons inherit semantic color from context:

• 14 line icons — arrow up/dn/flat, caret-dn, chev-lt/rt, check, info, warning, filter, search, refresh, grid, export
• 3 status dots (filled, semantic) — green / amber / red
• DAX SVG embedding pattern — inline path data, single-quoted XML attrs, currentColor inheritance, icon + text lockups
• Accessibility rules — never icon-only, <title> for standalone, 16px minimum render size, WCAG-compliant contrast against background

design-system/wordmark/ — Brand Wordmark

Light + dark wordmark SVGs (Contoso placeholder) with anatomy, clear-space rules, dimensions, placement in Power BI page headers, and the DAX SVG embedding pattern for dynamic headers.

---

Dependency map

tmdl-standards         ← syntax foundation
    └── measures       ← scalar DAX layer
            ├── calc-groups
            └── dax-udf

design-system          ← visual layer (independent)
    ├── iconography
    └── wordmark

Read tmdl-standards/SKILL.md first for the model layer; design-system/SKILL.md first for the visual layer.

---

Sample dataset — datamodel/

Contoso 10k-row sample, ready to load into Power BI:

File	Rows	Description
customer.csv	~10k	Customer dimension
product.csv	—	Product dimension
store.csv	—	Store dimension
date.csv	—	Date dimension
currencyexchange.csv	—	FX rates
sales.csv	—	Sales fact (header-level)
orders.csv	—	Order header
orderrows.csv	—	Order line items
contosoERD.png	—	Visual ERD of the model

Both the unpacked CSVs (datamodel/ContosoDatacsv-10k/) and the original .7z archive are included. Use the CSVs to test calc-groups, time-intelligence patterns, and currency conversion end-to-end.

---

Using the skills with Claude

1. Create a Claude.ai Project (or open an existing one).

2. Add the SKILL.md files as knowledge — at minimum tmdl-standards/SKILL.md, plus whichever others you need.

3. For design-system, also add the files in references/, iconography/, and wordmark/.

4. Prompt naturally:

   Write a Year-over-Year growth measure for Sales Amount, following the TMDL and measures skills.

   Create a Time Intelligence calculation group with None / YTD / PY / PY YTD / vs PY % items.

   Refactor these 12 individual time-intelligence measures into a single calc group.

   Audit this report against the design-system checklist and tell me what to fix.

Claude will return deployable TMDL blocks (with the createOrReplace wrapper) ready to paste into Power BI Desktop or Tabular Editor.

---

Conventions across all skills

• TAB indentation — never spaces.
• createOrReplace wrapper on every deployable block.
• Single quotes around any name containing spaces, dots, or apostrophes — 'Order Date', 'Customer''s Key'.
• Verbose, prefixed measure names — $ Revenue Net of Discounts, not $ Rev ND.
• LASTDATE('Date'[Date]) for rolling windows, never TODAY() (LASTDATE respects the visual filter).
• DIVIDE(num, den, 0) instead of / for safe division.

---

Versions

Skill	Version	Last updated
tmdl-standards	3.0	2026-05-02
measures	2.0	2026-05-02
calc-groups	1.5	2026-05-02
dax-udf	2.0	2026-05-02
design-system	2.2	2026-05-02
iconography	2.0	2026-05-02
wordmark	1.0	2026-05-02

---

License

MIT © Jonathan Papworth.