Copilot Customization

Create and manage GitHub Copilot rules, instructions files, and configuration for optimal AI assistance.

When to Use This Skill

• Setting up project-wide coding standards for Copilot
• Creating language-specific or folder-specific rules
• Configuring code review, commit message, or PR description instructions
• Choosing between instructions, skills, agents, and prompt files

Customization Hierarchy

┌─────────────────────────────────────────────────────────────────┐
│  INSTRUCTIONS (Rules & Guidelines)                              │
│  ├── .github/copilot-instructions.md  (global, auto-applied)   │
│  ├── .github/instructions/*.instructions.md (targeted, glob)   │
│  └── AGENTS.md (multi-agent compatible)                        │
│                                                                 │
│  SKILLS (Specialized Capabilities)                              │
│  └── .github/skills/*/SKILL.md (portable, on-demand)           │
│                                                                 │
│  PROMPT FILES (Reusable Prompts)                                │
│  └── .github/prompts/*.prompt.md (task automation)             │
│                                                                 │
│  AGENTS (Specialized Personas)                                  │
│  └── .github/agents/*.agent.md (roles with tools)              │
│                                                                 │
│  SETTINGS (VS Code Configuration)                               │
│  └── .vscode/settings.json (code review, commits, etc.)        │
└─────────────────────────────────────────────────────────────────┘

When to Use Each Option

Scenario	Format	File
Project-wide standards	Global	.github/copilot-instructions.md
Language-specific rules	Targeted	.github/instructions/*.instructions.md
Folder-specific guidelines	Targeted	.instructions.md with applyTo glob
Specialized capability	Skill	.github/skills/*/SKILL.md
Common task automation	Prompt	.github/prompts/*.prompt.md
Specialized AI persona	Agent	.github/agents/*.agent.md
Code review standards	Settings	reviewSelection.instructions
Commit message format	Settings	commitMessageGeneration.instructions

Instruction File Formats

Global Instructions

# Project Name - Copilot Instructions

## Technology Stack
| Tool | Purpose |
|------|---------|
| **Language** | Python 3.11+ |
| **Framework** | FastAPI |

## Coding Standards
- Use type hints on all functions
- Write docstrings for public APIs

## Don'ts
- ❌ Don't use `any` type
- ❌ Don't commit secrets

Targeted Instructions

---
name: Python Standards
description: Python coding standards for all Python files
applyTo: "**/*.py"
---

# Python Coding Standards

- Use type hints for all function parameters and return values
- Use dataclasses or Pydantic models for structured data
- Write Google-style docstrings for public functions

Glob Patterns for applyTo

Pattern	Matches
**/*.py	All Python files
**/*.{ts,tsx}	All TypeScript files
src/**	All files in src directory
**/test_*.py	All Python test files
frontend/**/*.tsx	React components in frontend

Settings-Based Instructions

Code Review

{
  "github.copilot.chat.reviewSelection.instructions": [
    { "file": ".github/instructions/code-review.instructions.md" }
  ]
}

Commit Messages

{
  "github.copilot.chat.commitMessageGeneration.instructions": [
    { "text": "Use conventional commits format: type(scope): description" },
    { "text": "Keep subject line under 50 characters" }
  ]
}

PR Descriptions

{
  "github.copilot.chat.pullRequestDescriptionGeneration.instructions": [
    { "text": "Include a summary of changes" },
    { "text": "List breaking changes if any" },
    { "file": ".github/instructions/pr-template.instructions.md" }
  ]
}

Layered Instructions Pattern

Combine global + targeted for comprehensive coverage:

.github/
├── copilot-instructions.md       # Universal project rules
└── instructions/
    ├── python.instructions.md    # applyTo: "**/*.py"
    ├── typescript.instructions.md # applyTo: "**/*.ts"
    ├── testing.instructions.md   # applyTo: "**/test_*"
    └── api.instructions.md       # applyTo: "src/api/**"

Rule Writing Principles

1. Be specific — Vague instructions produce vague results
2. Keep it short — Each instruction should be a single statement
3. Prioritize — Put most important rules first
4. Use examples — Show what good looks like
5. Be actionable — Focus on what to do, not just what not to do

Workflow

1. Analyze — Check existing customization files
2. Identify — Determine scope (global, language, folder)
3. Choose format — Global instructions, targeted, or settings
4. Write rules — Be specific, actionable, with examples
5. Validate — Test applyTo patterns match intended files

Guidelines

• No conflicting rules across files
• Settings reference correct file paths
• Instructions are clear and actionable
• Rules align with existing codebase patterns
• Related agents/skills reference the rules