| name | copilot-customization-selector |
| description | Help decide which GitHub Copilot customization to use (instructions, prompts, agents, or skills). Use this skill when users ask which customization type to create, want to understand the differences, or need guidance choosing between .instructions.md, .prompt.md, .agent.md, or SKILL.md files. |
Customization Selector
This skill helps you decide which GitHub Copilot customization option to use for your specific needs.
When to use this skill
- User asks "what type of customization should I create?"
- User wants to understand differences between instructions, prompts, agents, and skills
- User needs to choose the right approach for a new customization
- User asks "should I use a prompt or an instruction file?"
Quick Decision Flowchart
What do you want to achieve?
│
├─► Define coding standards/rules that apply automatically?
│ └─► Use CUSTOM INSTRUCTIONS (.instructions.md)
│
├─► Create a reusable task template (e.g., "generate tests")?
│ └─► Use PROMPT FILES (.prompt.md)
│
├─► Create a specialized AI persona with specific tools?
│ └─► Use CUSTOM AGENTS (.agent.md)
│
├─► Build portable capabilities with scripts/resources?
│ └─► Use AGENT SKILLS (SKILL.md)
│
└─► Connect external services or APIs?
└─► Use MCP SERVERS (mcp.json)
Decision Matrix
| Feature | Instructions | Prompt Files | Custom Agents | Agent Skills |
|---|
| File Extension | .instructions.md | .prompt.md | .agent.md | SKILL.md |
| Location | .github/instructions/ | .github/prompts/ | .github/agents/ | .github/skills/<name>/ |
| Triggers | Auto (always or via glob) | Manual (/name) | Manual (switch agent) | Auto (when relevant) |
| Can include scripts? | ❌ No | ❌ No | ❌ No | ✅ Yes |
| Can specify tools? | ❌ No | ✅ Yes | ✅ Yes | ❌ No |
| Can specify model? | ❌ No | ✅ Yes | ✅ Yes | ❌ No |
| Portable across tools? | ❌ VS Code only | ❌ VS Code only | ❌ VS Code only | ✅ Open standard |
| Status | Stable | Stable | Stable (1.106+) | Preview (1.108+) |
Detailed Guidance
Use Custom Instructions when
Perfect for:
- Enforcing coding standards across all requests
- Setting language/framework conventions (e.g., "always use TypeScript strict mode")
- Defining commit message or PR description guidelines
- Applying rules to specific file types via
applyTo glob patterns
- Sharing team coding practices in version control
File types:
| File | Location | Behavior |
|---|
copilot-instructions.md | .github/ | Applies to all requests |
*.instructions.md | .github/instructions/ | Conditional via applyTo |
AGENTS.md | Root or subfolders | Multi-agent compatible |
Example use cases:
- "Always use functional React components"
- "Follow PEP 8 for Python files"
- "Include JSDoc comments for all public functions"
- "Use conventional commits format"
Use Prompt Files when
Perfect for:
- Creating reusable workflows (e.g.,
/create-react-form, /security-review)
- Scaffolding components, API routes, or modules
- Generating tests with consistent patterns
- Running the same task repeatedly with variations
- Need to specify tools and agent for a specific task
Key features:
- Invoked with
/promptName in chat
- Can specify
agent, tools, and model in frontmatter
- Support variables like
${selection}, ${file}, ${input:name}
- Can reference instruction files for consistent guidelines
Example use cases:
/create-component - Generate a new React component with tests/code-review - Perform a security-focused code review/api-route - Scaffold a new API endpoint/migration-plan - Generate a database migration strategy
Use Custom Agents when
Perfect for:
- Creating specialized AI personas (planner, reviewer, architect)
- Restricting available tools (e.g., read-only for planning)
- Defining sequential workflows with handoffs
- Different tasks need different tool configurations
- Using a specific model for certain tasks
Key features:
- Define
tools list to control what the agent can do
- Use
handoffs for guided multi-step workflows
- Specify
model for optimal performance per task
- Set
infer: false to prevent use as subagent
Example agents:
- Planner - Read-only tools, generates implementation plans
- Reviewer - Focus on security vulnerabilities and code quality
- Architect - Design patterns and system architecture decisions
- Implementer - Full editing capabilities for coding tasks
Use Agent Skills when
Perfect for:
- Creating capabilities that work across VS Code, CLI, and coding agent
- Need to include scripts, examples, or resources
- Building specialized testing/debugging/deployment workflows
- Sharing capabilities with the community
- Want progressive loading (only loaded when relevant)
Key features:
- Open standard at agentskills.io
- Three-level loading: discovery → instructions → resources
- Can include scripts, templates, and example files
- Works across GitHub Copilot in VS Code, CLI, and coding agent
Example skills:
webapp-testing - Testing workflows with test templatesgithub-actions-debug - Debug CI/CD workflows with log analysisapi-documentation - Generate OpenAPI specs with examplesdatabase-migrations - Migration scripts with rollback templates
How They Work Together
┌─────────────────────────────────────────────────────────────┐
│ CUSTOM AGENT │
│ (defines persona, tools, model) │
│ ├── Can reference: Custom Instructions │
│ └── Can be triggered by: Prompt Files (via agent field) │
├─────────────────────────────────────────────────────────────┤
│ PROMPT FILE │
│ (defines reusable task template) │
│ ├── Can specify: agent, tools, model │
│ └── Can reference: Instructions via Markdown links │
├─────────────────────────────────────────────────────────────┤
│ CUSTOM INSTRUCTIONS │
│ (always applied guidelines, foundation layer) │
├─────────────────────────────────────────────────────────────┤
│ AGENT SKILLS │
│ (portable capabilities, auto-loaded when relevant) │
│ └── Works independently, loaded based on task context │
└─────────────────────────────────────────────────────────────┘
Recommended Folder Structure
.github/
├── copilot-instructions.md # Global project instructions
├── instructions/
│ ├── python.instructions.md # Python-specific (applyTo: **/*.py)
│ ├── typescript.instructions.md
│ └── security.instructions.md # Security guidelines
├── prompts/
│ ├── create-component.prompt.md
│ ├── code-review.prompt.md
│ └── generate-tests.prompt.md
├── agents/
│ ├── planner.agent.md # Read-only planning agent
│ ├── reviewer.agent.md # Code review agent
│ └── implementer.agent.md # Full coding agent
└── skills/
├── webapp-testing/
│ ├── SKILL.md
│ └── test-template.js
└── debugging/
└── SKILL.md
Common Combinations
Planning → Implementation Workflow
- Agent:
planner.agent.md with read-only tools
- Handoff: Button to switch to implementation agent
- Instructions: Shared coding standards apply to both
Consistent Test Generation
- Skill:
webapp-testing with test templates and utilities
- Prompt:
/generate-tests that references the skill patterns
- Instructions: Test naming conventions and coverage requirements
Security-First Development
- Instructions: Security guidelines applied globally
- Agent:
security-reviewer.agent.md for dedicated reviews
- Prompt:
/security-audit for on-demand security checks
Version Requirements
| Feature | Minimum VS Code Version | Setting |
|---|
copilot-instructions.md | 1.95 | github.copilot.chat.codeGeneration.useInstructionFiles |
*.instructions.md | 1.99 | Auto-discovered |
| Prompt files | 1.99 | Auto-discovered |
AGENTS.md | 1.102 | chat.useAgentsMdFile |
Custom agents (.agent.md) | 1.106 | Auto-discovered |
Nested AGENTS.md | 1.105 | chat.useNestedAgentsMdFiles (experimental) |
| Agent Skills | 1.108 | chat.useAgentSkills (preview) |
References
