GitHub Copilot Instructions vs Prompts vs Custom Agents vs Skills vs X vs WHY?

GitHub Copilot Instructions vs Prompts vs Custom Agents vs Skills vs X vs WHY? If you have been following my recent GitHub Copilot posts, you might have noticed a pattern. We have covered instructions, prompt files, skills, MCP, coding agents, and more. Each feature is powerful on its own. The confusing part is deciding which one to use for a specific problem. This post is your practical decision guide. We will compare: Custom Instructions Prompt Files Custom Agents Skills MCP Servers Hooks The 60-Second Cheat Sheet Primitive Typical location Scope Best for When not to use Custom Instructions .github/copilot-instructions.md , .github/instructions/*.instructions.md , AGENTS.md Always-on or pattern-based Team standards and default behaviour One-off tasks or named workflows Prompt Files .github/prompts/*.prompt.md Manual, on-demand slash command Repeatable one-shot tasks Multi-step runbooks with assets Custom Agents .github/agents/*.agent.md Selected agent mode/persona Specialised role pl