Agent Authoring

Agent Authoring Skill

Guidelines for creating and maintaining custom GitHub Copilot agents (.agent.md) tailored to this repository.

When to Use

• You need a new Copilot agent focused on a workflow (e.g., Storybook tests, log triage).
• You want to adjust tools/persona for existing agents.
• You are adding workspace-level agents under .github/agents or profile-level agents for reuse.

Quick Start

1. Create .github/agents/<agent-name>.agent.md (VS Code auto-detects this folder/extension).
2. Add YAML frontmatter with only supported fields: name, description, tools, target, infer, mcp-servers, handoffs.
3. In the body, write concise instructions: task focus, guardrails, run/validate steps, and handoffs.
4. Keep it under ~200-300 lines; link out to docs instead of pasting everything.

Frontmatter Cheatsheet

• name: Display name; defaults to file name if omitted.
• description: Placeholder text in chat input; keep short.
• tools: List allowed tools. For MCP servers, use <server>/* to include all tools or enumerate specific ones.
• target: github-copilot for Copilot agents (default), vscode for VS Code target.
• infer: Allow subagent use (default true). Set false if you want to restrict subagents.
• mcp-servers: For Copilot agents, point to MCP server configs (paths to server JSON). Use only if you need to pin servers.
• handoffs: Optional array of next-step buttons { label, agent, prompt?, send? }.

Body Structure (recommended)

• Purpose and scope: What this agent does and what it must not do.
• Operating defaults: Where to run commands, what to inspect first, preferred scripts.
• Playbooks: Ordered steps for common flows (run, debug, fix, validate).
• Guardrails: Safe-edit rules (scope, no unrelated changes, ask before destructive ops).
• Validation: How to verify work (tests/linters), how to summarize outputs.
• Links: Point to repo docs or skills for deeper detail.

Tool Selection Patterns

• Editing agent: include workspace, terminal, search; add fetch for docs; add MCP toolsets only if required.
• Read-only agent: omit editing tools; keep fetch/search.
• Narrow the tool list to prevent unsafe actions (e.g., no terminal for planning-only agents).

Handoffs

Use handoffs to guide sequential flows (e.g., Plan -> Implement -> Review). Keep labels short and make prompts actionable. Use send: false unless you want auto-submit.

Quality Bar

• Minimal, task-focused instructions; avoid boilerplate.
• No unsupported frontmatter fields (reject argument-hint, etc.).
• Prefer scoped commands over global installs; mention working directory if non-root.
• Add guardrails for destructive commands (never propose git reset --hard).
• Keep instructions ASCII and concise; use fenced code blocks for commands.

Validation Checklist

• Supported frontmatter only; fields spelled correctly.
• Tools list matches the agent’s intent; no over-broad capabilities.
• Clear run/validate steps with default commands.
• Guardrails called out.
• Links resolve (relative paths within repo or official docs).

Examples

• Location: .github/agents/storybook-interaction-tests.agent.md (interaction test fixer playbook).
• Planning agent: frontmatter with tools: ['fetch', 'search'], body instructs to gather context and produce a plan, handoff to implementation agent.

Maintenance Tips

• Keep agents in sync with repo workflows (scripts, test commands). Update after script changes.
• Remove stale handoffs when target agents are renamed or removed.
• Prefer additive changes; avoid reformatting existing agents without need.

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