Claude Ecosystem

Comprehensive guide for Claude Code CLI tool, extensibility (agents/skills/output styles), and CLAUDE.md architecture.

Module Selection

Quick Reference

Extension Types

Model Selection (Agents)

CLAUDE.md Token Budget

Extensibility Principles

Core Truths

Decision Heuristics

Activation Keywords

The description field is your activation gate. Include:

1. Task verbs: create, build, debug, fix, deploy
2. Problem descriptions: slow, broken, failing
3. Artifact types: component, API, database
4. Casual synonyms: "make it faster" → optimize

Common Workflows

Create Agent

---
name: agent-name
description: "Use when [use case]. PROACTIVELY for [triggers].\n\nExamples:\n<example>\nContext: [situation]\nuser: [request]\nassistant: [response]\n</example>"
tools: Grep, Glob, Read, Bash
model: haiku
---

# Agent Name

Mission statement.

## Strategy
[Approach]

## Does NOT Do
- [boundary] (use X instead)

Create Skill

---
name: skill-name
description: "[Core purpose]. [Technologies]. Capabilities: [list].
  Actions: [verbs]. Keywords: [triggers]. Use when: [scenarios]."
allowed-tools: Read, Grep, Glob
---

# Skill Name

## Patterns

### [Pattern Name]
**When you see:** [Observable trigger]
**This indicates:** [Expert insight]
**Therefore:** [Action]
**Watch out:** [Pitfall]

Initialize CLAUDE.md

1. Analyze codebase (language, framework, structure)
2. Extract code style, commands, patterns
3. Generate with template, customize
4. Validate commands, check token count
5. Target <400 lines, prefer <250

Detailed: references/initialization-workflow.md

Optimize CLAUDE.md

1. Evaluate token efficiency
2. Find redundancy, outdated info
3. Apply token reduction techniques
4. Target 40%+ reduction
5. Verify critical info retained

Detailed: references/optimization-patterns.md

Anti-Patterns

Quality Signals

Good Signs

• Frontmatter reads like "when to use" guide
• First 10 lines provide actionable guidance
• Expert would nod "yes, that's how I think"
• Explicit constraints on what it does NOT handle

Warning Signs

• 50% reference tables or field definitions

• No mention of "when NOT to use"
• Generic language for any domain
• Body exceeds 600 lines

References

CLI Tool

• references/getting-started.md - Installation, setup, auth
• references/slash-commands.md - Complete command catalog
• references/mcp-integration.md - MCP server configuration
• references/hooks-and-plugins.md - Hook types, plugin structure
• references/configuration.md - Settings hierarchy
• references/enterprise-features.md - IAM, SSO, sandboxing
• references/cicd-integration.md - GitHub Actions, GitLab CI
• references/ide-integration.md - VS Code, JetBrains
• references/advanced-features.md - Extended thinking, caching
• references/troubleshooting.md - Common issues
• references/api-reference.md - Admin, Messages, Skills APIs
• references/best-practices.md - Project organization, security
• references/agent-skills.md - Creating skills via CLI

Extensibility

• references/agent-development.md - Full YAML structure, system prompts
• references/skill-development.md - Structure, triggers, hooks

CLAUDE.md

• references/initialization-workflow.md - Creating new CLAUDE.md
• references/optimization-patterns.md - Token reduction techniques
• references/integration-strategies.md - Global config, MCP tools
• references/output-templates.md - Standard output formats

Related Skills

IMPORTANT: When creating/editing prompts, use prompt-architect skill.

Skill("prompt-architect") → Create/enhance skill/agent prompt content

Documentation:

• llms.txt: https://context7.com/websites/claude_en_claude-code/llms.txt?tokens=10000
• Main docs: https://docs.claude.com/en/docs/claude-code/
• GitHub: https://github.com/anthropics/claude-code