copilot-cli-plugin-builder

# Copilot CLI Plugin Builder Author GitHub Copilot CLI plugins — packages of skills, agents, hooks, and MCP servers distributed via marketplaces. ## Plugin Architecture Plugins are **file-based** (markdown + JSON). No compilation required. Two formats exist: | Format | Schema | Use | |--------|--------|-----| | **Agent Plugins 1.0** | `https://agent-plugins.org/schemas/1.0.0/plugin.schema.json` | Recommended — portable across Copilot CLI, Cursor, VS Code | | **Legacy** | No `$schema` | Still supported but not recommended for new plugins | Always use **Agent Plugins 1.0** unless the user has a specific reason for legacy format. ## Directory Layout (Agent Plugins 1.0) ``` my-plugin/ ├── plugin.json # Required manifest ├── skills/ # Portable skills │ └── skill-name/ │ └── SKILL.md # Skill definition ├── mcp.json # MCP server configs └── com.github.copilot/ # Copilot-specific components ├── agents/ │ └── my-agent.agent.md ├── commands/ ├── rules/ ├── hooks/ │ └── hooks.json └── lsp.json ``` Minimal plugin: just `plugin.json` + one component (skill, agent, hook, or MCP server). ## Workflow ### Phase 1: Gather Requirements Ask the user these questions (one at a time, skip if already specified): 1. **What should the plugin do?** — Get a clear purpose statement 2. **Which components?** — Skills, agents, hooks, MCP servers, or a combination? 3. **Plugin name?** — 1–64 chars, lowercase ASCII, digits, hyphens, periods If unsure about components, suggest the simplest approach: a single skill. ### Phase 2: Scaffold the Plugin Create the directory structure with `plugin.json`: ```json { "$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json", "name": "my-plugin", "version": "1.0.0", "description": "What this plugin does", "author": { "name": "Your Name" }, "license": "MIT", "keywords": ["relevant", "tags"] } ``` Then create each component. See the Component Guides below. ### Phase 3: Author Components #### Skills Skills inject context/instructions into the agent via `SKILL.md`: ```markdown --- name: my-skill description: When and why to use this skill --- # Instructions Be concise. Use imperative form. Include only what Claude doesn't already know. ``` Skills follow the same conventions as workspace skills (scripts/, references/, assets/ subdirectories). For skill authoring best practices, follow the skill-creator patterns. #### Custom Agents Agents are scoped sub-agents with isolated tools and prompts. Define as `.agent.md` files in `com.github.copilot/agents/`: ```markdown --- name: my-agent displayName: My Agent description: What this agent does (used by runtime for intent matching) tools: - grep - glob - view --- You are a specialized agent. Your role is to... ``` Or programmatically via the SDK — see `references/sdk-examples.md`. #### Hooks Hooks fire at lifecycle points. Create `com.github.copilot/hooks/hooks.json`: ```json { "version": 1, "hooks": { "sessionStart": [ { "type": "command", "command": "./scripts/init.sh", "timeout": 10 } ], "preToolUse": [ { "type": "command", "command": "./scripts/validate.sh", "timeout": 5 } ] } } ``` Available hooks: `sessionStart`, `sessionEnd`, `userPromptSubmitted`, `preToolUse`, `postToolUse`, `postToolUseFailure`, `errorOccurred`, `subagentStart`, `subagentStop`. For full details, see `references/hook-lifecycle.md`. #### MCP Servers External tool providers. Create `mcp.json` at plugin root: ```json { "$schema": "https://agent-plugins.org/schemas/1.0.0/mcp.schema.json", "mcpServers": { "my-server": { "type": "stdio", "command": "node", "args": ["${PLUGIN_ROOT}/server/index.js"], "env": { "DATA_DIR": "${PLUGIN_DATA}" } } } } ``` Transports: `stdio`, `streamable-http`, `sse` (deprecated). Variables: `${PLUGIN_ROOT}`, `${PLUGIN_DATA}`. ### Phase 4: Install and Test ```bash # Install locally copilot plugin install ./my-plugin # Verify copilot plugin list # Test in interactive session copilot # Then: /skills list, /agent, /plugin list ``` Plugins are cached — re-run `copilot plugin install ./my-plugin` after edits. ### Phase 5: Distribute **Local development:** ```bash copilot plugin install ./my-plugin ``` **From GitHub repo:** ```bash copilot plugin install OWNER/REPO copilot plugin install OWNER/REPO:PATH/TO/PLUGIN ``` **Via marketplace:** See `references/marketplace-guide.md` for creating and distributing through marketplaces. ## SDK Usage The `@github/copilot-sdk` provides programmatic control via JSON-RPC. Supports 6 languages: TypeScript, Python, Go, .NET, Rust, Java. Quick start (TypeScript): ```typescript import { CopilotClient, approveAll } from "@github/copilot-sdk"; const client = new CopilotClient(); await client.start(); const session = await client.createSession({ model: "auto", onPermissionRequest: approveAll, }); const response = await session.sendAndWait({ prompt: "Hello" }); console.log(response?.data.content); await client.stop(); ``` For SDK examples in all languages, custom tools, streaming, and MCP configuration, see `references/sdk-examples.md`. ## Component Reference | Component | Format | Location (Agent Plugins 1.0) | Purpose | |-----------|--------|------------------------------|---------| | Skill | `SKILL.md` | `skills/<name>/SKILL.md` | Inject context/instructions | | Agent | `.agent.md` | `com.github.copilot/agents/*.agent.md` | Scoped sub-agents | | Hook | `hooks.json` | `com.github.copilot/hooks/hooks.json` | Lifecycle callbacks | | MCP Server | `mcp.json` | `mcp.json` | External tool providers | ## Key Concepts - **Agent Plugins 1.0** is the portable, cross-client standard from `agent-plugins.org` - **Legacy Copilot Extensions** (GitHub App–based) were sunset November 10, 2025 — do not reference them - The old `gh copilot` extension was deprecated October 25, 2025 — replaced by standalone `copilot` CLI - Plugins are **file-based** — no compilation or build step required - The SDK manages CLI process lifecycle automatically ## References - `references/plugin-manifest.md` — Full manifest schema, fields, and validation - `references/sdk-examples.md` — SDK usage in all 6 languages with custom tools, streaming, MCP - `references/hook-lifecycle.md` — All 9 hook types with input/output signatures - `references/marketplace-guide.md` — Creating and distributing through marketplaces