copilot-security-instructions: Skill for Claude Code

Markdown Customizations Skill

Purpose

Help create and maintain Copilot customization files with correct structure and consistent, high-signal instructions.

When to use

Use this skill when working on any of:

• agents/*.agent.md
• prompts/*.prompt.md
• instructions/*.instructions.md
• skills/**/SKILL.md

Procedure

1. Identify the target file type and verify the correct path + extension.
2. Add YAML frontmatter at the top with required keys.
3. Write the body using this structure:
   • # Title
   • ## Purpose
   • ## How to use
   • ## Rules (MUST/SHOULD/MAY)
   • ## Examples (at least one when ambiguity is likely)
4. Validate glob patterns for .instructions.md files.
5. Ensure no contradictions with repo-wide copilot-instructions.md.

Do / Don’t

Do

• Use short, testable rules (e.g., “MUST include description in agent profiles”).
• Provide one minimal realistic example for each “pattern” (agent/prompt/instructions/skill).
• Use fenced code blocks with yaml or md tags.

Don’t

• Don’t put YAML anywhere except the initial frontmatter block.
• Don’t create skill.md; the file must be named SKILL.md.
• Don’t introduce conflicting guidance across multiple instruction files.

Examples

Agent profile frontmatter example

---
name: my-agent
description: Short description of what this agent does
tools: ["read", "search", "edit"]
---

Path-specific instructions frontmatter example

---
applyTo: ".github/prompts/**/*.prompt.md"
excludeAgent: "code-review"
---

Prompt file frontmatter example

---
agent: "agent"
description: "One-line description of what this prompt does"
---