compose-skill / rules

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

# Reference File Writing Standards

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

## File Structure

1. **Line 1: `# Title`** — concise topic name
2. **Next line: `Load when: …`** (or `Load this when …`) — the task that needs this file, in one line
3. **Optional `## Choose`** — a short yes/no decision tree when the file covers a real choice
4. **Rule sections** — numbered rules: bold rule, one-line reason, `*Prevents:*` the failure it stops; tag `(non-negotiable)` or `(default)` where it matters
5. **`## Red flags`** (when real rationalizations exist) — `| Thought | Reality |` table, first-person thought → rebuttal citing the rule number
6. **`## Verification`** — checkbox gates, each a command or a yes/no condition
7. **No long Table of Contents** — agents navigate by headings; a file well past 100 lines may open with a 5–10 line contents list

## 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 WRONG/RIGHT code pair | Three paragraphs describing the concept |
| No tutorial content | Show the pattern/pitfall | Explain what `StateFlow` or `PagingSource` is |
| Third-party APIs as gotchas | One line naming the API + "verify against current docs" | Setup walkthroughs, pinned versions |
| Trim filler words | Direct statements | "It is important to note that...", "In order to...", "You should consider..." |

## DRY Cross-Referencing

Each rule has ONE canonical home. Other files point to it instead of duplicating; a pointer into another skill names that skill.

| Concept | Canonical home | Other files do |
|---|---|---|
| MVI contract, `BaseViewModel`, effects, collection at the Route | `compose-architecture/references/mvi-contract.md` | One-line rule + pointer |
| State ownership, drafts, `SavedStateHandle` | `compose-architecture/references/state-ownership.md` | Pointer |
| Failure types, `launchGuarded`, UI error tiers | `compose-architecture/references/error-handling.md` | Pointer |
| Flows, scopes, dispatchers | `compose-architecture/references/coroutines-flow.md` | Pointer |
| Koin modules, lifetimes, ViewModel params | `compose-architecture/references/dependency-injection.md` | 1–2 line binding example + pointer |
| Navigation 3 keys, back stack, results | `compose-architecture/references/navigation.md` | Pointer |
| Existing Hilt / MVVM / Navigation 2 projects | `compose-architecture/references/existing-projects.md` | Pointer |
| ViewModel test setup, fakes, test dispatchers | `compose-feature/references/testing.md` | Domain-specific fake + pointer |

## Section Templates

### Rule

```markdown
3. (non-negotiable) **Transport failures propagate to `launchGuarded`; no repository `catch` swallows them.** The ViewModel's `onError` picks the tier. *Prevents:* stale data with no message and no retry.
```

### Red flags

```markdown
## Red flags

| Thought | Reality |
|---|---|
| "I'll swallow the timeout so the UI stays calm." | No. Rule 3: the ViewModel's `onError` decides the tier. |
```

### Verification

```markdown
## Verification

- [ ] `rg -n "catch \(" <feature-root>/data` shows no catch that drops a transport failure: yes or no.
```

## Code Examples

- Use WRONG/RIGHT 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
- No pinned dependency versions; say where to verify (`gradle/libs.versions.toml`, official release notes)

## Token Budget

- Target: **under 3,000 tokens** per reference file (hard max: 4,500)
- Estimate: characters / 4
- If a file grows past the target, split it by topic into two references, each with its own `Load when` line

## Checklist for New Reference Files

- [ ] `# Title` plus a one-line `Load when`
- [ ] Numbered rules with `*Prevents:*`; no tutorial content
- [ ] Tables instead of multi-paragraph prose
- [ ] WRONG/RIGHT code examples for key pitfalls
- [ ] `## Verification` checklist; `## Red flags` where real rationalizations exist
- [ ] Pointers to canonical homes (no duplicated rules)
- [ ] Under 3,000 tokens
- [ ] Listed in the owning `SKILL.md` `## Reference lookup` with when to load it