Rule Author

Canonical workflow, templates, and references for authoring AI coding assistant rules. Supports GitHub Copilot, Cursor, and Claude Code.

Internal skill. Users interact via the fusion-rules gateway, which routes to editor-specific agents that follow the workflow defined here.

Scope

This skill provides:

Workflow (Steps 1–7 below) — the guided authoring process
Templates (assets/) — starter files for each editor format
References (references/) — tech-stack examples

It does not provide agents. Agents live in fusion-rules/agents/ and reference this skill's assets and workflow.

Required inputs

Mandatory

Repository context (working directory or repo URL)

Gathered during interview

Tech stack (languages, frameworks, build tools)
Code conventions (naming, formatting, patterns)
Testing expectations (framework, coverage, style)
Documentation preferences (comments, TSDoc/JSDoc, README standards)
Commit and PR conventions
Error handling patterns
Security or compliance constraints
File/path-specific conventions that need scoped rules

Instructions

Step 1 — Assess current state

Check the repository for existing rule files:

.github/copilot-instructions.md
.github/instructions/*.instructions.md
.cursor/rules/*.md
.cursor/rules/*.mdc
.cursor/rules/**/*.md
.cursor/rules/**/*.mdc
CLAUDE.md
.claude/CLAUDE.md
.claude/rules/*.md
.claude/rules/**/*.md

Report what exists, what is missing, and whether updates or new files are needed.

Step 2 — Scan repository

Before interviewing, scan the repository for existing documentation and configuration that encodes conventions. Extract actionable directives from:

Documentation files:

README.md — project overview, setup instructions, tech stack
CONTRIBUTING.md — code style, PR workflow, commit conventions
AGENTS.md, CLAUDE.md — existing AI instructions
docs/adr/**, adr/**, docs/decisions/** — Architecture Decision Records
docs/**/*.md — any developer guides, onboarding docs, style guides
SECURITY.md — security policies and constraints
CODE_OF_CONDUCT.md — collaboration guidelines (rarely rule-relevant)

Configuration files:

package.json / pyproject.toml / *.csproj — tech stack, scripts, dependencies
tsconfig.json / jsconfig.json — language settings, strictness
biome.json / .eslintrc* / .prettierrc* / ruff.toml / .editorconfig — formatting and linting rules
.github/workflows/*.yml — CI checks, required validations, test commands
Dockerfile / docker-compose.yml — runtime environment
Makefile / Justfile / Taskfile.yml — build and task commands

Code patterns (sample, do not exhaustively read):

Entry points (src/index.*, src/main.*, app.*) — architecture patterns
Test files — testing framework, naming conventions, file placement
Directory structure — architectural boundaries, feature organization

For each source, extract:

Concrete conventions that can become imperative directives
Build/test/lint commands the AI should know
Architecture boundaries or patterns to follow
Explicit "do this / don't do that" rules

Skip:

Implementation details that change frequently
Content that restates language/framework defaults
Aspirational rules not enforced by CI or team practice

Present a summary of discovered conventions to the developer, organized by area, before proceeding to the interview.

Step 3 — Interview (fill gaps)

Use the scan results to skip areas already well-documented. Ask focused questions only for gaps. Cover these areas one at a time:

Tech stack — languages, frameworks, runtime, package manager
Code style — naming conventions, formatting rules, import ordering
Architecture — project structure, key patterns (MVC, hexagonal, etc.)
Testing — framework, conventions, coverage expectations
Documentation — inline comments style, doc generation, README standards
Git workflow — branch naming, commit message format, PR expectations
Security — sensitive data handling, auth patterns, compliance rules
Path-specific concerns — any directories or file types that need specialized guidance

For each area, present what the scan found and ask: "Is this accurate? Anything to add or correct?" Do not re-ask for information already captured.

For each convention that needs deeper context, use the follow-up questions in assets/creation-follow-up.md — purpose, exceptions, boundaries, voice.

Step 4 — Classify guidance

Separate the gathered conventions into buckets:

GitHub Copilot:

Bucket	Target file	When it activates
Always-on conventions	`.github/copilot-instructions.md`	Every Copilot interaction
Scoped conventions	`.github/instructions/<name>.instructions.md`	Only when matching files are open/referenced

Cursor:

Bucket	Target file	When it activates
Always-on conventions	`.cursor/rules/<name>.mdc` with `alwaysApply: true`	Every Cursor Agent session
Auto-attached conventions	`.cursor/rules/<name>.mdc` with `globs`	When matching files are in context
Agent-selected conventions	`.cursor/rules/<name>.mdc` with `description` only	When the Agent decides it is relevant
Manual conventions	`.cursor/rules/<name>.mdc` (no `alwaysApply`, no `globs`)	Only when @-mentioned in chat

Claude Code:

Bucket	Target file	When it activates
Always-on conventions	`CLAUDE.md` or `.claude/CLAUDE.md`	Every Claude Code session
Scoped conventions	`.claude/rules/<name>.md` with `paths` frontmatter	When Claude reads matching files
Unconditional rule	`.claude/rules/<name>.md` (no `paths`)	Every session (like always-on)

Decision rule: If a convention applies to all files in the repo, it belongs in root / always-on instructions. If it applies only to specific paths or file types, create a scoped rule.

When targeting multiple editors, generate parallel files with equivalent content — do not duplicate guidance within a single editor's files.

Step 5 — Draft rule files

Generate files using the templates in assets/:

GitHub Copilot:

For root instructions: use assets/copilot-instructions-template.md as the starting structure
For scoped instructions: use assets/scoped-rule-template.md and fill in the correct applyTo glob pattern

Cursor:

For always-on or scoped rules: use assets/cursor-rule-template.mdc and set frontmatter accordingly

Claude Code:

For project instructions: use assets/claude-rule-template.md as the starting structure
For scoped rules: place in .claude/rules/ with paths frontmatter

Quality rules (enforced during drafting):

Keep instructions concise — aim for actionable directives, not explanations
Use imperative voice ("Use camelCase for variables", not "Variables should use camelCase")
Avoid duplicating guidance between root and scoped files
Validate applyTo / globs / paths glob patterns match the intended files
Warn if total root instructions exceed ~80 lines (risk of context dilution)
Warn if a scoped instruction file exceeds ~50 lines (GitHub Copilot), ~500 lines (Cursor), or ~200 lines (Claude Code CLAUDE.md)
See references/examples.md for concrete good and bad examples
See assets/quality-checklist.md for the full checklist

Step 6 — Review and refine

Present the drafted files to the developer for review. For each file:

Show the full content
Highlight any quality warnings (length, broad globs, duplication)
Ask for approval or edits

Step 7 — Write files

After approval, write the rule files to the repository. Create the .github/instructions/, .cursor/rules/, and/or .claude/rules/ directories as needed.

Confirm the final file list and paths before writing.

Expected output

.github/copilot-instructions.md — root instructions file (created or updated)
.github/instructions/*.instructions.md — zero or more scoped instruction files
.cursor/rules/*.mdc — zero or more Cursor rule files (when Cursor is targeted)
CLAUDE.md or .claude/CLAUDE.md — project instructions (when Claude Code is targeted)
.claude/rules/*.md — zero or more Claude Code scoped rule files
Summary of what was created/updated and why

Instructions vs skills vs rules — when to use which

Need	GitHub Copilot	Cursor	Claude Code
Always-on coding conventions	`copilot-instructions.md`	`.cursor/rules/*.mdc` with `alwaysApply: true`	`CLAUDE.md`
File/path-specific guidance	`.github/instructions/*.instructions.md`	`.cursor/rules/*.mdc` with `globs`	`.claude/rules/*.md` with `paths`
Task-specific multi-step workflows	A skill (`SKILL.md`)	`.cursor/rules/*.mdc` (manual or agent-selected)	Skills / subagents
Agent routing and orchestration	Agent definitions (`.agent.md`)	`.cursor/rules/*.mdc` with `description`	Subagent configs
Simple project-wide instructions	`copilot-instructions.md`	`AGENTS.md`	`CLAUDE.md`

Instructions and rules shape how the AI writes code. Skills define what it can do as structured tasks.

Safety and constraints

Never:

Embed secrets, tokens, or credentials in rule files
Generate rules that contradict repository security policies
Overwrite existing files without showing the diff and getting approval
Invent conventions — only document what the developer confirms

Always:

Show drafts before writing any files
Validate glob patterns against actual repository paths
Warn on overly broad globs (e.g., **/* captures everything)
Keep instructions concise and actionable
Preserve existing content when updating (append or merge, never replace silently)

References

references/examples.md — concrete examples for different tech stacks
assets/creation-follow-up.md — per-rule follow-up questions (purpose, exceptions, boundaries, voice)
assets/frontmatter-scenarios.md — scenario-based frontmatter guide for GitHub Copilot, Cursor, and Claude Code
assets/copilot-instructions-template.md — starter template for root instructions
assets/scoped-rule-template.md — starter template for scoped rules
assets/cursor-rule-template.mdc — starter template for Cursor rules
assets/claude-rule-template.md — starter template for Claude Code rules
assets/quality-checklist.md — quality review checklist

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