Choose the Right Claude Extension Surface

## TL;DR

Use the smallest Claude extension surface that fits the job:

- **Skill**: reusable expertise, standards, or process knowledge.
- **Slash command**: a user-triggered workflow shortcut.
- **Hook**: deterministic automation around a Claude Code lifecycle event.
- **Subagent**: delegated specialist work with its own focus and context.
- **MCP server**: live tools, resources, or external systems.
- **Settings**: project or user policy that should apply consistently.

When two surfaces could work, choose the one with less runtime authority. A
static skill or slash command is usually easier to review than a hook or MCP
server because it does not add live access by itself.

## Prerequisites & Requirements

- [ ] {"task": "Workflow is named", "description": "You can describe the repeated task in one sentence"}
- [ ] {"task": "Sharing scope is known", "description": "The extension is personal, project-local, team-shared, or organization-managed"}
- [ ] {"task": "Access needs are mapped", "description": "You know whether the workflow needs prompts only, repository files, commands, or external systems"}
- [ ] {"task": "Risk is understood", "description": "You know whether the workflow can read data, write files, call tools, or run automatically"}

## Core Concepts Explained

### Skills package reusable expertise

Choose a skill when Claude needs durable guidance: domain conventions, review
criteria, migration steps, testing heuristics, or a playbook that should travel
between sessions. Skills are a good fit when the main value is knowledge and
instructions rather than a live integration.

### Slash commands package repeatable prompts

Choose a slash command when a human should intentionally start a workflow with a
short command. They are useful for recurring tasks such as review checklists,
release notes, triage prompts, migration planning, or issue analysis.

### Hooks package deterministic automation

Choose a hook when something should happen at a lifecycle point without a user
typing a prompt each time. Hooks are best for narrow, predictable automation:
notifications, formatting checks, logging, guardrails, or context reminders.

### Subagents package delegated specialist work

Choose a subagent when Claude should hand a task to a focused specialist. A
subagent can carry a narrower role, review lens, or domain focus than the main
conversation. Use this when separation of attention matters.

### MCP packages live capability

Choose MCP when Claude needs to interact with tools, resources, APIs, databases,
files, or services through a protocol boundary. MCP is the right surface for
live data and actions, but it also deserves the most access review.

### Settings package policy

Choose settings for behavior that should apply consistently across the user or
project environment: allowed tools, model preferences, permissions, or team
defaults. Settings are not a workflow by themselves; they shape the environment
where workflows run.

## Step-by-Step Decision Guide

1. **Start with the output.** If the workflow produces advice, a checklist, a
   review, or a plan, start with a skill or slash command. If it must interact
   with live systems, consider MCP.

2. **Decide who starts it.** If a human should opt in each time, use a slash
   command. If the behavior should apply automatically at a lifecycle point,
   use a hook.

3. **Decide whether expertise should travel.** If the workflow is mostly
   reusable know-how, package it as a skill. A skill can include process,
   examples, rubrics, and references without creating a live integration.

4. **Decide whether work needs delegation.** If the task benefits from a
   specialist role or separate focus, use a subagent. This is useful for code
   review, test planning, security triage, documentation review, or domain
   analysis.

5. **Decide whether Claude needs live capabilities.** If Claude must read a
   resource, call an API, query a database, inspect an issue tracker, or invoke
   a tool, use MCP and review the exposed tools/resources.

6. **Put policy in settings.** If the question is "what should Claude be allowed
   to do here?" instead of "what workflow should Claude run?", use settings.

7. **Combine surfaces only when needed.** A slash command can call on a skill; a
   subagent can use MCP tools; a hook can remind Claude about policy. Keep each
   layer small enough that a teammate can review it.

## Decision Matrix

| Need | Best surface | Why |
| --- | --- | --- |
| Reusable domain guidance | Skill | Durable instructions and examples without live access |
| Repeatable manual workflow | Slash command | Human-triggered and easy to discover |
| Automatic lifecycle behavior | Hook | Runs at a defined event instead of relying on memory |
| Focused delegated analysis | Subagent | Keeps a specialist role and context separate |
| Live tools or external data | MCP | Standard surface for tools/resources/services |
| Consistent project policy | Settings | Applies defaults and permission boundaries |

## Review Checklist

- [ ] {"task": "Smallest surface", "description": "The extension does not add automation or live access unless needed"}
- [ ] {"task": "Clear owner", "description": "A person or team owns updates and review"}
- [ ] {"task": "Sharing scope", "description": "Personal, project, team, or organization scope is documented"}
- [ ] {"task": "Access review", "description": "Hooks and MCP tools are reviewed for files, commands, services, and side effects"}
- [ ] {"task": "Discoverability", "description": "Teammates can find and understand the extension"}
- [ ] {"task": "Rollback path", "description": "The extension can be disabled, removed, or replaced safely"}

## Troubleshooting

- **The workflow is becoming too broad**: split it into a skill for reusable
  knowledge plus a slash command for the entry point.
- **A hook is doing too much**: move judgment-heavy work into a command or skill
  and keep the hook deterministic.
- **An MCP server is used only for static text**: replace it with a skill or
  command unless live resources are actually required.
- **Subagents overlap heavily**: merge roles or define sharper handoff criteria.
- **Settings hide project behavior**: document the policy in the repository so
  teammates understand what applies automatically.

## Duplicate Check

This guide is a decision framework for choosing between Claude Code extension
surfaces. Existing entries cover individual commands, hooks, agents, skills, and
MCP servers, but they do not provide a source-backed comparison that helps teams
choose the smallest appropriate surface for a workflow.

## References

- Claude Code subagents - https://code.claude.com/docs/en/sub-agents
- Claude Code skills - https://code.claude.com/docs/en/skills
- Claude Code slash commands - https://code.claude.com/docs/en/slash-commands
- Claude Code hooks - https://code.claude.com/docs/en/hooks
- Claude Code MCP - https://code.claude.com/docs/en/mcp
- Claude Code settings - https://code.claude.com/docs/en/settings