AI Instruction File Standards Guide

Language: English | 繁體中文

Version: 2.0.0 Last Updated: 2026-04-28 Applicability: All AI coding tools

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Core Standard: This skill implements AI Instruction File Standards. For comprehensive methodology documentation, refer to the core standard.

AI Skills Hierarchy | AI 技能層級

This skill is part of a three-layer AI collaboration system:

Layer	Skill	Question it Answers
Behavior (Immediate)	/ai-collaboration	"How should AI respond accurately?"
Configuration (Session)	/ai-instruction-standards (this)	"What to write in CLAUDE.md / AGENTS.md?"
Architecture (Long-term)	/ai-friendly-architecture	"How to structure code for AI?"

Purpose

This skill helps create and maintain AI instruction files with proper separation between universal standards and project-specific configurations, across all major AI coding tools.

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Quick Reference

Supported AI Tools (2026-04-28)

CLI / Agent Tools (Terminal)

Tool	Primary File	Workflow Mechanism	MCP
Claude Code	CLAUDE.md + .claude/rules/*.md	Skills (.claude/skills/ → /{name})	✅
Gemini CLI	GEMINI.md	.gemini/commands/*.toml → /{name}	✅
OpenAI Codex CLI	AGENTS.md (+ AGENTS.override.md)	Team commands; /review built-in	✅
OpenCode	AGENTS.md (CLAUDE.md compatible)	Built-in only (/init /undo /share)	✅

AI-native IDE / Editor Integration

Tool	Primary File	Workflow Mechanism	MCP
Cursor	.cursor/rules/*.mdc ⚠️	@-mentions; /multitask	✅
GitHub Copilot	.github/copilot-instructions.md	.github/prompts/*.prompt.md → /{name}	✅
Windsurf	.windsurfrules / .windsurf/rules/*.md	.windsurf/workflows/*.md → /{name}	✅
Cline	.clinerules	None	✅

⚠️ Cursor: .cursorrules is deprecated — migrate to .cursor/rules/*.mdc

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Cross-Tool Universal Standard: AGENTS.md

AGENTS.md is the emerging de-facto cross-tool instruction standard:

Supported by: Gemini CLI, OpenAI Codex CLI, OpenCode, GitHub Copilot, Windsurf, Cursor Not supported by: Claude Code (uses CLAUDE.md), Cline (uses .clinerules)

Recommendation: Use AGENTS.md as the universal baseline for cross-tool projects, then add tool-specific files for advanced features (Skills, Workflows, Prompts).

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Core Principle: Universal vs Project-Specific

Type	Contains	Example
Universal	Generic rules	"Run tests before committing"
Project-Specific	Concrete commands	"Run npm test before committing"

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Recommended Layout

# [Project Name] - AI Instructions

## Universal Standards
<!-- Rules applicable to ANY project -->
- Commit message format
- Code review checklist
- Testing standards
- Anti-hallucination rules

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## Project-Specific Configuration
<!-- Unique to THIS project -->

### Tech Stack
[Your technologies here]

### Quick Commands
[Your build/test/deploy commands]

### File Structure
[Your project structure]

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Tool-Specific Setup Guides

Claude Code

CLAUDE.md                        # Main instructions (hierarchical: global → project → subdir)
.claude/rules/                   # Glob-scoped additional rules
.claude/skills/{name}/SKILL.md   # Custom slash commands → /{name}
.claude/agents/{name}.md         # Subagent definitions

Gemini CLI

GEMINI.md                          # Main instructions
.gemini/commands/{name}.toml       # Custom slash commands → /{name}
.gemini/agents/{name}.yaml         # Subagent definitions

Example .gemini/commands/review.toml:

description = "Run code review checklist"
prompt = "Review the following changes: !{git diff HEAD}"

OpenAI Codex CLI

AGENTS.md                  # Main instructions (Git root → cwd traversal)
AGENTS.override.md         # Temporary override (highest priority)
~/.codex/AGENTS.md         # Global fallback
.codex/agents/             # Custom agent definitions

OpenCode

AGENTS.md                       # Primary (auto-recognized)
CLAUDE.md                       # Also recognized (migration compatibility)
.opencode/agents/               # Custom agent definitions
opencode.json (instructions)    # Glob-pattern file references

Cursor

.cursor/rules/                  # MDC format rules (replaces .cursorrules)
  {name}.mdc                    # Frontmatter: description, globs, alwaysApply
AGENTS.md                       # Also supported for agent context

MDC frontmatter example:

---
description: "TypeScript coding standards"
globs: ["**/*.ts", "**/*.tsx"]
alwaysApply: false
---

Migration: If you have .cursorrules, move content to .cursor/rules/*.mdc.

GitHub Copilot

.github/copilot-instructions.md         # Always-on, all chats
.github/instructions/*.instructions.md  # File-glob scoped (applyTo frontmatter)
.github/prompts/*.prompt.md             # Reusable templates → /{name} slash commands
.github/agents/*.agent.md               # Custom agents with tool access control
AGENTS.md                               # Also recognized

Windsurf

.windsurfrules                   # Project rules (team-shareable)
.windsurf/rules/*.md             # MDC frontmatter structured rules
.windsurf/workflows/*.md         # Reusable task sequences → /{name}
AGENTS.md                        # Also recognized

Workflow example (.windsurf/workflows/review.md):

Run a code review:
1. Run `git diff HEAD`
2. Check for BLOCKING issues (security, correctness)
3. Check for IMPORTANT issues (design, tests)
4. Output findings with BLOCKING/IMPORTANT/SUGGESTION prefixes

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Multi-Tool Project Configuration

When a project uses multiple AI tools:

project/
├── AGENTS.md                            # Universal baseline (cross-tool)
├── CLAUDE.md                            # Claude Code (extends AGENTS.md)
├── GEMINI.md                            # Gemini CLI
├── .cursor/rules/
│   └── standards.mdc                    # Cursor
├── .windsurf/
│   └── workflows/                       # Windsurf workflows
│       ├── review.md
│       └── checkin.md
└── .github/
    ├── copilot-instructions.md          # Copilot always-on
    └── prompts/
        └── review.prompt.md             # Copilot slash command

Best Practice: Write universal content in AGENTS.md once, then import/reference it from tool-specific files to avoid duplication.

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Content Guidelines

Universal Content (Keep Generic)

Category	Good Examples
Commit Standards	"Follow Conventional Commits format"
Code Review	"Use BLOCKING, IMPORTANT, SUGGESTION prefixes"
Testing	"Maintain 80% coverage minimum"
AI Behavior	"Always read code before analyzing"

Avoid in Universal Sections:

• Specific commands (npm test, pytest)
• Hardcoded paths (cli/src/, /var/www/)
• Version numbers (Node.js 18, Python 3.11)
• Project names and URLs

Project-Specific Content

Category	Examples
Tech Stack	Node.js 18, React 18, PostgreSQL 15
Commands	npm run lint, ./scripts/deploy.sh
File Structure	src/, cli/, tests/
Team Conventions	Traditional Chinese comments

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Maintenance Checklist

Before committing changes to AI instruction files:

• Universal sections contain no project-specific paths, commands, or versions
• Project-specific sections are clearly marked
• Cross-references to standards documents are correct
• Format matches existing sections
• If using Cursor: .cursorrules migrated to .cursor/rules/*.mdc
• If multi-tool project: AGENTS.md covers the universal baseline

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Configuration Detection

Detection Order

1. Check for existing CLAUDE.md, AGENTS.md, GEMINI.md, or equivalent files
2. Detect which AI tools are in use (check for .cursor/, .windsurf/, .github/copilot-instructions.md, etc.)
3. Analyze content structure for universal/project-specific separation
4. If not found, suggest creating structured AI instruction file

First-Time Setup

If no AI instruction file found:

1. Ask: "This project doesn't have an AI instruction file. Which AI tools do you use?"
2. Recommend AGENTS.md for cross-tool projects, CLAUDE.md for Claude Code only
3. Determine project type and tech stack
4. Generate template with appropriate sections
5. Add to .gitignore if contains sensitive info

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Next Steps Guidance

After /ai-instruction-standards completes, suggest:

• Create or update project's CLAUDE.md / AGENTS.md ⭐ Recommended — Apply standards immediately
• Run /ai-friendly-architecture to optimize AI collaboration at the architecture level
• Run /ai-collaboration to review AI behavior guidelines

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Related Standards

• AI Instruction File Standards - Core standard
• Documentation Writing Standards - Writing guidelines
• Anti-Hallucination Guidelines - AI accuracy rules
• AI-Friendly Architecture - Context optimization

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Version History

Version	Date	Changes
2.0.0	2026-04-28	Add Gemini CLI, OpenAI Codex CLI; update Cursor (MDC format, deprecated .cursorrules); update OpenCode (AGENTS.md primary); update Copilot (multiple file types); update Windsurf (Workflows); add AGENTS.md cross-tool standard section
1.0.0	2026-01-25	Initial release

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License

This skill is released under CC BY 4.0.

Source: universal-dev-standards