---
description: Token-optimized writing standards for skill reference files. Apply when creating or editing reference .md files in the references/ directory.
globs: references/*.md
alwaysApply: false
---

# Reference File Writing Standards

Every reference file must be token-efficient. Agents already know standard APIs — provide patterns, pitfalls, and project-specific rules, not tutorials.

## File Structure

1. **Line 1: `# Title`** — concise topic name
2. **Line 2-3: One-liner scope** — what this file covers and when to use it, not a marketing paragraph
3. **Cross-links** — point to related canonical files (e.g., "For shared architecture concepts, see [architecture.md](architecture.md)")
4. **`References:` block** (optional) — external URLs for provenance; keep, they're cheap
5. **No Table of Contents** — agents navigate by headings, not TOC lists

## Writing Rules

| Rule | Do | Don't |
|---|---|---|
| Tables over prose | `\| Issue \| Fix \|` table | Multi-paragraph explanations |
| Rules over explanations | State the rule directly | Explain "why" unless non-obvious |
| Examples over descriptions | One BAD/GOOD code pair | Three paragraphs describing the concept |
| No tutorial content | Show the pattern/pitfall | Explain what `StateFlow` or `PagingSource` is |
| One-liner intros | "SQLite persistence via Room (KMP-ready since 2.7.0)" | "Room is a powerful persistence library that provides an abstraction layer over SQLite..." |
| Trim filler words | Direct statements | "It is important to note that...", "In order to...", "You should consider..." |

## DRY Cross-Referencing

Each concept has ONE canonical home. Other files link to it instead of duplicating.

| Concept | Canonical home | Other files do |
|---|---|---|
| MVI ViewModel collection pattern | `architecture.md` § Reactive Data Collection | 5-8 line domain stub + cross-link |
| State modeling (forms, calculators) | `architecture.md` § State Modeling | Cross-link |
| Effect delivery (Channel vs SharedFlow) | `architecture.md` § Effect Delivery | Cross-link |
| Generic test setup (runTest, Turbine) | `testing.md` | Domain-specific test factory + cross-link |
| Koin module patterns | `koin.md` | 1-2 line binding example + cross-link |
| Hilt module patterns | `hilt.md` | 1-2 line binding example + cross-link |
| Nav 3 + DI wiring | `navigation-3-di.md` | Condensed example + cross-link |

## Section Templates

### MVI Integration (in data-layer files)

Keep to ~5-8 lines: state the domain-specific mapping rule + cross-link.

```markdown
## MVI Integration

Map entities to domain models at the repository boundary. Never pass raw [DataType] to the UI.

For the ViewModel collection pattern, see [architecture.md](architecture.md) — Reactive Data Collection.
```

### DI Integration (in data-layer files)

1-2 line binding examples + link.

```markdown
## DI Integration

Always provide [Type] as a **singleton**.

\`\`\`kotlin
// Koin: single<Type> { createType(get()) }
// Hilt: @Provides @Singleton fun provideType(...): Type = ...
\`\`\`

For full module patterns, see [koin.md](koin.md) or [hilt.md](hilt.md).
```

### Anti-Patterns (table format)

```markdown
## Anti-Patterns

| Anti-pattern | Why it is harmful | Better replacement |
|---|---|---|
| [pattern] | [consequence] | [fix] |
```

### Performance / Critical Rules (table format)

```markdown
## Critical Rules

| Rule | Why |
|---|---|
| [rule] | [brief rationale] |
```

## Code Examples

- Use BAD/GOOD pairs — show the mistake and the fix side by side
- No redundant comments like `// Import the module` — only explain non-obvious intent
- Keep examples minimal: show the pattern, not a full app
- Use `<latest>` for dependency versions with a comment: `// search: "library latest version"`

## Token Budget

- Target: **under 3,500 tokens** per reference file (hard max: 4,000)
- Estimate: characters / 4
- If a file grows past 3,500 tokens, split into base + advanced (e.g., `animations.md` + `animations-advanced.md`)

## Checklist for New Reference Files

- [ ] One-liner scope, no marketing intro
- [ ] No Table of Contents
- [ ] Tables instead of multi-paragraph prose
- [ ] BAD/GOOD code examples for key pitfalls
- [ ] Anti-patterns table at the end
- [ ] Cross-links to canonical homes (no duplicated patterns)
- [ ] MVI/DI/Testing sections use stubs + cross-links
- [ ] Under 3,500 tokens
- [ ] Linked from `SKILL.md` (both trigger list and reference catalog)