Extensibility — Skills, Hooks, MCP, Plugins

This group covers the four ways to extend Claude Code’s behavior beyond its built-in capabilities. It explains, concept-first, the flow of modularizing expertise with skills, attaching automation to events with hooks, connecting external tools with MCP, and shipping all of it as one package with plugins.

Background reference

This page is background material on Claude Code itself, the platform MoAI-ADK runs on. MoAI-ADK’s own features are covered in the sections above it in the sidebar.

These four are exactly the materials for building an Agentic Harness. In harness engineering — designing an environment where the agent works well instead of writing the code yourself — skills carry the agent’s knowledge, hooks carry deterministic discipline, MCP carries the connection to the outside world, and plugins carry the deployment unit for the combination. What MoAI-ADK deploys with a single moai init, and what /moai project generates project-specifically, are ultimately combinations of these materials.

Info

One-line summary: Once you understand the four extension points — skills, hooks, MCP, and plugins — you can turn Claude Code into a harness unique to your project.

Understand it with an analogy

Keep these four straight with one picture. A hook is an automatic-door sensor — a defined action fires by itself when an event occurs. A skill is a manual you pull out only when needed — normally just the cover (a one-line description) is visible, and the body opens when the job arrives. MCP is the standard power socket for plugging in external tools, and a plugin is the package that ships all three in one box.

flowchart TD
    A[Skills
Expertise modules] --> B[Hooks
Event-driven automation]
    B --> C[MCP Servers
External tool connections]
    C --> D[Plugins and Marketplaces
Extension package distribution]

We recommend reading in this order: start with skills, the lightest extension point, then hooks for automation, MCP for connecting to the outside world, and finally plugins, which bundle them for distribution. Skills, hooks, and MCP link deeply into the MoAI-ADK advanced documents, so grasp the concepts first and dig deeper afterwards.

Once you know the four materials, head to the next group, Agents and Automation, to see how to run agentic loops on top of the harness built from them.