Agent Development for Claude Code Plugins
Overview
Agents are autonomous subprocesses that handle complex, multi-step tasks independently. Understanding agent structure, triggering conditions, and system prompt design enables creating powerful autonomous capabilities.
**Key concepts:**
- Agents are FOR autonomous work, commands are FOR user-initiated actions
- Markdown file format with YAML frontmatter
- Triggering via description field with examples
- System prompt defines agent behavior
- Model and color customization
Agent File Structure
Complete Format
---
name: agent-identifier
description: Use this agent when [triggering conditions]. Examples:
<example>
Context: [Situation description]
user: "[User request]"
assistant: "[How assistant should respond and use this agent]"
<commentary>
[Why this agent should be triggered]
</commentary>
</example>
<example>
[Additional example...]
</example>
model: inherit
color: blue
tools: ["Read", "Write", "Grep"]
---
You are [agent role description]...
**Your Core Responsibilities:**
1. [Responsibility 1]
2. [Responsibility 2]
**Analysis Process:**
[Step-by-step workflow]
**Output Format:**
[What to return]Frontmatter Fields
name (required)
Agent identifier used for namespacing and invocation.
**Format:** lowercase, numbers, hyphens only **Length:** 3-50 characters **Pattern:** Must start and end with alphanumeric
**Good examples:**
- `code-reviewer`
- `test-generator`
- `api-docs-writer`
- `security-analyzer`
**Bad examples:**
- `helper` (too generic)
- `-agent-` (starts/ends with hyphen)
- `my_agent` (underscores not allowed)
- `ag` (too short, < 3 chars)
description (required)
Defines when Claude should trigger this agent. **This is the most critical field.**
**Must include:**
- Triggering conditions ("Use this agent when...")
- Multiple `<example>` blocks showing usage
- Context, user request, and assistant response in each example
- `<commentary>` explaining why agent triggers
**Format:**
Use this agent when [conditions]. Examples:
<example>
Context: [Scenario description]
user: "[What user says]"
assistant: "[How Claude should respond]"
<commentary>
[Why this agent is appropriate]
</commentary>
</example>
[More examples...]**Best practices:**
- Include 2-4 concrete examples
- Show proactive and reactive triggering
- Cover different phrasings of same intent
- Explain reasoning in commentary
- Be specific about when NOT to use the agent
model (required)
Which model the agent should use.
**Options:**
- `inherit` - Use same model as parent (recommended)
- `sonnet` - Claude Sonnet (balanced)
- `opus` - Claude Opus (most capable, expensive)
- `haiku` - Claude Haiku (fast, cheap)
**Recommendation:** Use `inherit` unless agent needs specific model capabilities.
color (required)
Visual identifier for agent in UI.
**Options:** `blue`, `cyan`, `green`, `yellow`, `magenta`, `red`
**Guidelines:**
- Choose distinct colors for different agents in same plugin
- Use consistent colors for similar agent types
- Blue/cyan: Analysis, review
- Green: Success-oriented tasks
- Yellow: Caution, validation
- Red: Critical, security
- Magenta: Creative, generation
tools (optional)
Restrict agent to specific tools.
**Format:** Array of tool names
tools: ["Read", "Write", "Grep", "Bash"]**Default:** If omitted, agent has access to all tools
**Best practice:** Limit tools to minimum needed (principle of least privilege)
**Common tool sets:**
- Read-only analysis: `["Read", "Grep", "G
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