Composability Primitives

Claude Code has four composable primitives: Skills, Commands, MCPs, and Sub-agents. They can be combined for powerful workflows.

These four building blocks are designed to be mixed and matched. A skill can trigger an MCP, which spawns a sub-agent, which runs a command. Understanding this composability is key to building powerful, automated workflows.

Skills are saved workflows. Do a task once, then tell Claude to save it as a skill so you can rerun it with a single command.

Example: Fetch Hacker News articles → save summary to local directory. Tell Claude "save what we just did as a skill called fetch-hackernews." Behind the scenes, it's just an MD file with a system prompt that Claude recognizes and can invoke later.

Skills and commands are now interchangeable. Skills automatically become slash commands for quick invocation.

Recent Anthropic change merged skills and commands. When you create a skill, it's automatically available as a slash command (e.g., /fetch-hackernews). This makes invoking workflows fast and natural.

Always ask Claude to create, update, and manage your skills and commands. Don't manually edit the MD files.

Stay in the habit of having Claude manage its own configuration. To extend a skill: "Extend fetch-hackernews to also pull from Twitter and Apple News." Claude will update the underlying system prompt file correctly.