Cross-Agent Compatibility

The Open Standard

SKILL.md is an open format. A single skill file works across multiple AI coding agents:

Agent	Skill Location	Format
Claude Code	`.claude/skills/` or `~/.claude/skills/`	`SKILL.md` native
GitHub Copilot	`.github/skills/` or `~/.copilot/skills/`	`SKILL.md` native
Cursor	`.cursor/rules/`	SKILL.md adapted as rule files
Windsurf	`.windsurf/rules/`	SKILL.md adapted as rule files
Gemini CLI	`.gemini/skills/` or install from repo	`SKILL.md` native
Kiro IDE	`.kiro/skills/` (project or global)	`SKILL.md` native + `AGENTS.md`
OpenCode	via `AGENTS.md` + `skill` tool	agent-driven execution
Codex CLI	`AGENTS.md` + repository instructions	SKILL-like workflows expressed as instructions

Setup Per Agent

Claude Code

mkdir -p .claude/skills/tdd
cp SKILL.md .claude/skills/tdd/

Auto-discovers skills in .claude/skills/. Personal skills in ~/.claude/skills/.

Key capabilities: full host-level access — scripts, network, filesystem.

Plugin install (from marketplace):

/plugin marketplace add addyosmani/agent-skills
/plugin install agent-skills@addy-agent-skills

GitHub Copilot

mkdir -p .github/skills/tdd
cp SKILL.md .github/skills/tdd/

Project: .github/skills/. Personal: ~/.copilot/skills/.

Cursor

Uses .cursor/rules/ with .mdc (Markdown Cursor) files:

mkdir -p .cursor/rules

Each .mdc file has YAML frontmatter controlling activation:

---
description: "TDD workflow for test-first development"
globs: ["src/**/*.ts", "tests/**/*.ts"]
alwaysApply: false
---
# Instructions here (paste SKILL.md body)

Activation Mode	When Loaded
Always (`alwaysApply: true`)	Every session
Auto (agent decides)	Agent matches by description
Globs	File pattern match (e.g. `*.tsx`)
Manual	Only when @-mentioned

Priority: Team Rules > Project (.cursor/rules/) > User (Settings) > .cursorrules (legacy).

Windsurf

mkdir -p .windsurf/rules
cp SKILL.md .windsurf/rules/tdd.md

Auto-discovers rules in .windsurf/rules/.

Gemini CLI

Native skills installation:

gemini skills install https://github.com/addyosmani/agent-skills.git --path skills

Or from local clone:

gemini skills install ./agent-skills/skills/

Also supports persistent context via GEMINI.md.

Kiro IDE

mkdir -p .kiro/skills/tdd
cp SKILL.md .kiro/skills/tdd/

Supports both project-level and global skills. Also reads AGENTS.md.

OpenCode

Uses AGENTS.md at repo root + agent-driven skill tool for execution.

Install via npx (Community Skills)

npx skills@latest add mattpocock/skills/tdd
npx skills@latest add mattpocock/skills/write-a-prd

Rules Files Across Agents

Beyond skills, each agent reads a project-wide rules file:

Agent	Rules File
Claude Code	`CLAUDE.md`
Cursor	`AGENTS.md` + `.cursor/rules/*.md` (may require explicit context include in some setups)
Windsurf	`.windsurfrules`
GitHub Copilot	`.github/copilot-instructions.md`
OpenAI Codex	`AGENTS.md`
Gemini CLI	`GEMINI.md`

Runtime Differences

Capability	Claude Code	Claude API	Copilot	Cursor	Gemini CLI
Network access	full	none	host-dep	host-dep	full
Script execution	full	pre-installed	host-dep	host-dep	full
Package install	local only	none	host-dep	host-dep	local only
Sharing scope	personal/project	workspace/org	repo/user	repo/user	personal/project

Design skills for the most constrained runtime first, then add capabilities.

Portable Skill Design

Two-layer architecture for cross-agent portability:

skills/
  my-skill/
    core/
      SKILL.md          ← platform-agnostic
      references/
      schema/
    adapters/
      claude-code/      ← Claude-specific wrappers
      copilot/          ← Copilot-specific wrappers
      cursor/           ← Cursor-specific rules format

The core/ layer works everywhere. The adapters/ layer handles platform differences.

Skill Registries and Collections

Registry	Description	Size
skills.sh	Community registry	thousands of indexed skills
addyosmani/agent-skills	Production engineering workflows	20 skills, 12k+ stars
mattpocock/skills	Planning, dev, tooling, writing	19 skills, 14k+ stars
hoodini/ai-agents-skills	Curated for Copilot/Claude/Cursor/Windsurf	25+ skills
Anthropic pre-built	PowerPoint, Excel, Word, PDF	4 official skills