Quick Decision Framework
Is it a single, focused capability?
├─ YES: Does Claude need to decide when to use it?
│ ├─ YES → Skill
│ └─ NO → Slash Command (user controls timing)
└─ NO: Do you need parallel execution or context isolation?
├─ YES → Subagents
└─ NO → Are you bundling multiple extensions?
├─ YES → Plugin
└─ NO → Use MCP Server for external tools