Extending on Claude Code Wiki

Subagents, Skills, and MCP Servers: Architecture Deep Dive

Mon, 01 Jan 0001 00:00:00 +0000

Subagents, Skills, and MCP Servers: Architecture Deep Dive#

Executive Summary#

Claude Code extends capabilities through three distinct mechanisms with different isolation models, memory characteristics, and context window implications:

Aspect	Subagents	Skills	MCP Servers
Purpose	Task delegation with reasoning	Knowledge/workflow injection	External tool/API access
Reasoning	Full AI (isolated instance)	Inherits main instance	None (deterministic)
Memory	Session-based, resumable	Shared with main	Stateless per call
Context	Own isolated window	Injected into main	Minimal overhead
Invocation	Explicit (Task tool)	Auto-discovered	Explicit tool calls
State	Fresh but resumable	Part of main conversation	Truly stateless

Table of Contents#

Subagents, Skills, and MCP Servers: Architecture Deep Dive

Subagents (Task Tool)#

What They Are#

Subagents are specialized AI assistants spawned via the Task tool. Each operates as an independent Claude instance with its own conversation context.

Building Custom Subagents & Skills: Extending Claude Code

Mon, 01 Jan 0001 00:00:00 +0000

Building Custom Subagents & Skills: Extending Claude Code#

Executive Summary#

Claude Code’s capabilities can be extended through custom subagents (autonomous task executors with isolated context), skills (injected instructions that guide behavior), and plugins (packages that bundle everything together). This article covers how to build each from scratch – file structures, YAML configuration, tool permissions, model selection, and the architectural patterns that make extensions effective.

Extension	What It Is	File Location	When It Runs
Subagent	Isolated AI worker	`.claude/agents/*.md`	When Claude delegates a task
Skill	Injected instructions	`.claude/skills/*/SKILL.md`	Auto-discovered or `/invoked`
Plugin	Packaged bundle of all three	Plugin marketplace or local	When plugin is enabled

Table of Contents#

Building Custom Subagents & Skills: Extending Claude Code

Subagents#

What Subagents Are#

A subagent is an isolated AI worker that Claude delegates tasks to. Each subagent gets its own context window, its own system prompt, and a defined set of tools. When Claude spawns a subagent, the main conversation’s context is protected – the subagent does its work, returns a result, and that result is all that enters the main context.

Custom Hooks Cookbook: Practical Recipes for Automating Claude Code

Mon, 01 Jan 0001 00:00:00 +0000

Custom Hooks Cookbook: Practical Recipes for Automating Claude Code#

Executive Summary#

Hooks let you run code at specific points in Claude Code’s lifecycle – before a tool runs, after a file is edited, when a session starts, when Claude finishes responding. This cookbook provides copy-paste-ready recipes for the most common use cases: auto-formatting, command safety, test gates, notifications, logging, and context injection. Each recipe includes the hook configuration, the script, and notes on gotchas.

Integration Patterns: Connecting Claude Code with External Tools and Services

Mon, 01 Jan 0001 00:00:00 +0000

Integration Patterns: Connecting Claude Code with External Tools and Services#

Executive Summary#

Claude Code connects to external systems through four integration mechanisms: MCP servers for tool access, hooks for workflow automation, headless mode for CLI scripting, and GitHub Actions for CI/CD. Each serves a different purpose and operates at a different layer. This article covers when to use each, how they work, and practical patterns for combining them.

Mechanism	Purpose	Direction	Runs When
MCP servers	Connect external tools/data	Claude calls out	Claude decides to use it
Hooks	Automate around Claude’s work	System calls scripts	Lifecycle events fire
Headless mode	Script Claude from outside	External calls in	Your script invokes it
GitHub Actions	CI/CD automation	Events call Claude	GitHub events trigger it

Table of Contents#

Integration Patterns: Connecting Claude Code with External Tools and Services

The Integration Landscape#

Claude Code integrates with external systems through four distinct mechanisms. Each operates at a different layer and serves a different purpose:

Agent Teams: Multi-Agent Orchestration in Claude Code

Mon, 01 Jan 0001 00:00:00 +0000

Agent Teams: Multi-Agent Orchestration in Claude Code#

Executive Summary#

Agent teams let multiple Claude Code instances work together on complex tasks. One session acts as team lead, coordinating work and assigning tasks. Teammates work independently in their own context windows, communicate through direct messaging, and share a task list. This is an experimental feature (disabled by default) that’s most valuable for tasks that benefit from parallel work, competing perspectives, or specialized roles.