Chapter 5 · Tour · 12 min read

The ecosystem

Claude Code alone is a good agent. With the ecosystem, it becomes a platform you extend instead of wait for.

This chapter is a tour with enough steps to try each piece yourself. Skim it, pick one thing, come back later for depth.

Everything we're about to cover — skills, plugins, MCPs, subagents — runs inside sessions. The app keeps several open at once, so one conversation can be mid-refactor while another is still planning.

Skills

A skill is a bundle of instructions + optional scripts that Claude loads on demand. A domain-specific playbook — lives in ~/.claude/skills/, activates automatically when the situation matches.

An example worth a look: visualize ↗. Takes any markdown document — a plan, a brainstorm, an architecture doc — and turns it into a polished, shareable HTML artifact. One well-defined job, well-scoped instructions, a few helper scripts. The shape of a good skill.

Open standard. Skills follow the Agent Skills open format ↗ — spec is public, skills are portable across Claude Code and other tools that adopt the standard. Anthropic maintains a reference repo ↗ with 17 production skills you can read as exemplars.

Chapter 6 shows how to have Claude build one of these for you.

→ Skills docs ↗

Plugins

A plugin bundles related skills, commands, and hooks into one installable unit. Install once, get the whole workflow.

Chapter 6 walks through installing and using the Compound Engineering plugin ↗ — Avery's full brainstorm → plan → work → review → compound loop. That's the one to try first. Super Powers ↗ is another worth knowing about — a broader pick-and-choose toolkit.

As a reference point: the Heart of Gold toolkit ↗ is a small collection of skills I bundled for my daily work (visualize is one of them). Not something to install now — an example of what emerges once you've written three or four skills you don't want to lose. You'll build one of your own.

→ Plugins docs ↗

Build your first skill — the agentic way

Before you install more of other people's, write one of your own. When something repeats — the shape of the prompt, the format of the output, the sequence of steps — extract a skill. And don't hand-write SKILL.md. Have Claude do it.

Two meta-skills that write skills

Both do the same job: guide you through discovery, draft a well-shaped SKILL.md, write it to disk. Pick one.

• skill-creator — shipped by Anthropic in the anthropics/skills ↗ repo. Install via /plugin from that marketplace. Canonical, minimal, teaches the shape.
• craft-skill — part of the Heart of Gold toolkit ↗. Opinionated, five-phase workflow with a technique checklist, higher-conformance output by default.

The walkthrough

With either installed, in a real project, run:

/skill-creator

(or /craft-skill, depending on which you installed).

Claude asks, one question at a time:

1. What should this skill do? One sentence. "Turn a markdown brainstorm into a shareable HTML visual artifact."
2. When should it activate? Trigger phrases. "visualize, mindmap, show me the structure, make this visual."
3. Who's the user? Specific. "Me, when I've finished a brainstorm and want to share the shape with someone."
4. What does success look like? The output shape. "A single HTML file, dashboard-style layout, that I can copy to share."

Answer each as specifically as you can. Vague answers make vague skills.

Claude then drafts the SKILL.md — name, a description with those triggers in it, bounded tool allowlist, mission, boundaries, decision rules, examples. Shows you the diff. You review, tweak, accept.

The file lands in ~/.claude/skills/my-skill/SKILL.md. Next session, when you say one of the trigger phrases, the skill activates automatically.

Progressive disclosure

Skills stay under ~500 lines. Longer content goes into bundled files: references/ for reading material, scripts/ for helpers, assets/ for templates. This is called progressive disclosure — the metadata is always loaded, the body loads when triggered, the extras load only if needed.

A mature skill like visualize in the Heart of Gold toolkit ↗ shows what that looks like at scale — one SKILL.md, half a dozen helper scripts beside it, decision trees for when each script applies. None of it was hand-written cold; each piece got added when a week of use revealed a gap.

Agent Skills open format

The format is an open spec ↗ — frontmatter fields, loader behaviour, progressive-disclosure rules. Anthropic's full reference is in anthropics/skills/spec/agent-skills-spec.md ↗. Skills you write work in Claude Code today and will work in any tool that adopts the spec tomorrow.

The endgame

Do this three or four times — extract a skill whenever something repeats — and suddenly you have a small collection. Bundle them with a .claude-plugin/plugin.json, publish to GitHub, and that's your plugin. Same shape as the Compound Engineering plugin you installed earlier, just yours. Your team installs once and inherits everything you've learned to systematise.

That's compound, all the way down.

→ Skills docs ↗ · Plugins docs ↗

MCPs — Claude's hands on external services

Model Context Protocol is the open standard for wiring Claude to tools that live outside its conversation — filesystems, databases, browsers, APIs. If skills extend what Claude knows, MCPs extend what Claude can do.

Try one: Chrome DevTools MCP

The standout for web work. Gives Claude live access to Chrome — console logs, network requests, Lighthouse, performance traces, screenshots.

claude mcp add --transport stdio chrome-devtools -- npx -y chrome-devtools-mcp@latest

Then in your session:

Open https://example.com and tell me why its LCP is slow. Run Lighthouse if you need to.

Claude opens the page, inspects, reports back. This is the moment MCPs stop being abstract.

Others worth knowing about

• Gmail, Google Drive, Calendar, Notion — bundled on claude.ai for plan users
• Postgres, Linear, Sentry, GitHub, Playwright — community MCPs, one claude mcp add away
• Build your own — mcp-builder skill in anthropics/skills scaffolds one

Security note. MCPs that fetch untrusted content (web pages, issues, emails) can inject instructions into your session. Anthropic's warning stands: third-party MCPs at your own risk. Chapter 8.5 has more.

→ MCP docs ↗

Subagents — delegate to keep your context clean

A subagent is a specialised worker Claude spawns with its own context window, tools, and permissions. When Claude needs to do something heavy — explore a big codebase, run a review, summarise a long file — it can delegate to a subagent instead of burning your main context.

You can invoke them directly, or let Claude choose.

Try one: the built-in Explore agent

Ship-built. Read-only, fast (Haiku), ideal for "where is X?" questions in a large codebase.

In any repo, ask:

Use the Explore agent to find where authentication is handled, then summarise.

Or more explicitly, mention it by name:

@Explore: find every place we call the Stripe API.

Your main conversation gets a two-paragraph summary. The actual file-reading happened in a side context that's now discarded. You spent ~100 tokens on the result, not ~20k on the exploration.

Create your own

For recurring delegation — say, a reviewer that always applies your team's standards — run:

/agents

Choose Library → Create new agent → let Claude generate the definition. Scope it (Personal or Project), restrict its tools, save. Your agent is now .claude/agents/my-agent.md and available via @my-agent or natural language.

Note. In Claude Code v2.1.63+, the internal Task tool was renamed to Agent. Older tutorials calling it Task still work — same thing.

Limit. Subagents cannot spawn other subagents. For nested delegation, use skills with context: fork or chain from the main conversation.

→ Subagents docs ↗

Remote and mobile — Claude off your desk

Two different products people confuse. Both need a Pro plan or higher — API-key-only setups are locked out.

Remote Control — your workstation, your files

Claude Code runs on your machine, with full local filesystem access, your configured MCPs, your keys. You drive it from a browser or mobile app.

Setup — four steps:

1. Confirm version: claude --version (needs 2.1.51+)
2. claude → /login to sign in through claude.ai
3. In your project: claude --remote-control "My Project"
4. Press spacebar at the terminal → QR code. Scan with the Claude mobile app (iOS ↗, Android ↗) or open claude.ai/code in a browser.

You can now drive the session from anywhere. Long-running builds, PR reviews from a meeting, "check the deploy" from your phone.

Claude Code on the Web — cloud-hosted, ephemeral

Different product. Session runs on Anthropic-managed VMs, starting from a fresh clone of your GitHub repo. No local files, no local MCPs. Good for quick GitHub-based tasks from any device.

Start via claude.ai/code on the web — pick a repo, start a session.

Mobile app

Not a standalone Claude Code — a controller for Remote Control sessions and Claude Code on the Web. Push notifications for permission prompts. Review diffs, chat, approve tool calls from your phone. Starts web sessions on its own.

→ Remote Control docs ↗ · Claude Code on the Web ↗

Practice: continue your sample

Working through the lab in order? Take what this chapter taught to the sample you started in chapter 2 — or to a codebase of your own, where it'll land harder.

1. Install one of the meta-skills from this chapter: /plugin install skill-creator from anthropics/skills, or the Heart of Gold toolkit for /craft-skill. Pick one.
2. Run it and let it walk you through authoring a skill called scaffold-endpoint. Purpose: add a new GET /<name> route matching your project's framework conventions — minimal-API MapGet in Varianta A, @app.get in Varianta B, or whatever your own repo uses. Trigger phrases: scaffold endpoint, add a new route.
3. Once saved, trigger the skill in your project — ask it to add GET /ping returning { "pong": true }. Review the output. If the scaffolding is off, edit the skill, not the output. That's the feedback loop.

When it works: you have a reusable skill you didn't hand-write, living in ~/.claude/skills/ or your project's .claude/skills/. The next chapter's practice runs the full Compound Engineering loop on one real feature.

The ecosystem is a menu, not a checklist. Install what actually saves you time. Everything else can wait.