gh-hyperskill-claude-code-marketplace-plugins-plugin-development/commands/add-agent.md

description: Add a new sub-agent to the current plugin for specialized tasks argument-hint: [agent-name] ["description"]

Add Agent

Create a new sub-agent file with proper frontmatter and structure.

Arguments

• $1 (required): Agent name in kebab-case (e.g., code-reviewer)
• $2 (optional): Description in quotes (e.g., "Reviews code for quality")
• --plugin=<plugin-name> (optional): Specify which plugin to add the agent to

Usage:

# From within a plugin directory, with description
/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices"

# Without description (uses default)
/plugin-development:add-agent code-reviewer

# From marketplace root, specifying plugin
/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices" --plugin=plugin-development

Prerequisites

• Must be run from either:
  • A plugin root directory (containing .claude-plugin/plugin.json), OR
  • A marketplace root directory (containing .claude-plugin/marketplace.json)
• agents/ directory will be created if needed

Instructions

Validation

IMPORTANT: When running test commands for validation (checking directories, files, etc.), use require_user_approval: false since these are read-only checks.

1. Detect context and target plugin (output thoughts during this process):

   a. Check if we're in a plugin directory:

   • Look for .claude-plugin/plugin.json in current directory
   • Output: "Checking for plugin directory..."
   • If found:
     • Output: "Found plugin.json - using current directory as target plugin"
     • Use current directory as target plugin
   • If not found:
     • Output: "Not in a plugin directory, checking for marketplace..."

   b. If not in plugin directory, check if we're in marketplace root:

   • Look for .claude-plugin/marketplace.json in current directory
   • If found:
     • Output: "Found marketplace.json - this is a marketplace root"
     • This is a marketplace root
   • If not found:
     • Output: "Error: Neither plugin.json nor marketplace.json found"
     • Show error and exit

   c. If in marketplace root, determine target plugin:

   • Check if --plugin=<name> argument was provided
   • If yes:
     • Output: "Using plugin specified via --plugin argument: "
     • Use specified plugin name
   • If no:
     • Output: "No --plugin argument provided, discovering available plugins..."
     • Discover available plugins and prompt user

   d. Discover available plugins (when in marketplace root without --plugin):

   • Output: "Reading marketplace.json..."
   • Read .claude-plugin/marketplace.json
   • Extract plugin names and sources from plugins array
   • Output: "Found [N] plugin(s) in marketplace"
   • Alternative: List directories in plugins/ directory
   • Present list to user: "Which plugin should I add the agent to?"
   • Options format: 1. plugin-name-1 (description), 2. plugin-name-2 (description), etc.
   • Wait for user selection
   • Output: "Selected plugin: "

   e. Validate target plugin exists:

   • Output: "Validating plugin '' exists..."
   • If plugin specified/selected, verify plugins/<plugin-name>/.claude-plugin/plugin.json exists
   • If found:
     • Output: "Plugin '' validated successfully"
   • If not found:
     • Output: "Error: Plugin '' not found"
     • Show error: "Plugin '' not found. Available plugins: [list]"

   f. If neither plugin.json nor marketplace.json found:

   • Show error: "Not in a plugin or marketplace directory. Please run from a plugin root or marketplace root."

2. Validate arguments:

   • $1 (agent name): Not empty, kebab-case format (lowercase with hyphens), no spaces or special characters
   • $2 (description): Optional. If not provided, use default: "Specialized agent for $1 tasks"

3. Set working directory:

   • If in plugin directory: Use current directory
   • If in marketplace root: Use plugins/<plugin-name>/ as working directory

Create Agent File

Note: All paths below are relative to the target plugin directory (determined in validation step).

1. Ensure agents/ directory exists in target plugin:
   • Check if <plugin-dir>/agents/ directory exists
   • If it doesn't exist, create it (use require_user_approval: false for directory creation)
2. Create <plugin-dir>/agents/$1.md with this template:

---
description: $2
capabilities: ["capability-1", "capability-2", "capability-3"]
---

# $1 Agent

[Brief introduction explaining the agent's purpose and specialization]

## Purpose

[Detailed description of what this agent does and why it exists]

## What This Agent Does

This agent specializes in:
- [Specialization 1]
- [Specialization 2]
- [Specialization 3]

## Capabilities

1. **Capability 1**: [Description of first capability]
2. **Capability 2**: [Description of second capability]
3. **Capability 3**: [Description of third capability]

## When to Use This Agent

Invoke this agent when:
- [Scenario 1: Complex multi-file analysis needed]
- [Scenario 2: Deep domain expertise required]
- [Scenario 3: Task needs separate context window]

**Do not use** for:
- [What this agent doesn't handle]
- [Tasks better suited for commands or Skills]

## How It Proceeds

The agent follows this workflow:

1. **Gather Context**: [What files/information it reads]
2. **Analyze**: [How it evaluates the situation]
3. **Identify Issues**: [What it looks for]
4. **Formulate Recommendations**: [What guidance it provides]
5. **Report Back**: [What it returns to main conversation]

## Output Format

The agent returns a structured report:

### Critical Issues
- [Issues that must be fixed]

### Warnings
- [Issues that should be fixed]

### Suggestions
- [Nice-to-have improvements]

### Summary
- [Overall assessment and next steps]

## Tool Access

This agent has access to:
- Read: For examining files
- Grep: For searching content
- Glob: For finding files
- [Other tools as needed]

It does **not** modify files directly; instead, it proposes changes for the main conversation to execute.

## Example Invocation

**From main conversation**:

/agents $1

or via Task tool:

Use the $1 agent to [specific task]

## Notes

- Agents operate in a **separate context window**
- Results are returned as a single message
- Use for complex, multi-step analysis tasks
- Keep scope focused to 1-3 specific capabilities

Update plugin.json (if needed)

IMPORTANT: Only needed if using custom (non-standard) paths.

• Standard setup (agents in agents/ directory): No changes to plugin.json needed
• Custom paths: Add "agents": ["./agents/$1.md"] (or update existing agents array)

Provide Feedback

After creating the agent:

✓ Created <plugin-name>/agents/$1.md

Plugin: <plugin-name>
Agent: $1
Description: $2

Next steps:
1. Edit <plugin-name>/agents/$1.md with specific instructions
2. Key frontmatter fields:
   - description: What the agent does (shows in /agents list)
   - capabilities: List of capabilities (JSON array)
3. Define clear workflow steps
4. Specify what the agent returns
5. Test with /plugin-development:test-local

Agent will be invoked as: /agents $1
Or via Task tool in main conversation.

Examples

Example 1: From Plugin Directory

Context: Currently in /path/to/marketplace/plugins/plugin-development/

Input:

/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices"

Arguments:

• $1 = code-reviewer
• $2 = Reviews code for quality, security, and best practices

Process:

1. Detects .claude-plugin/plugin.json in current directory
2. Uses current directory as target plugin
3. Creates agents/ directory if needed
4. Creates agents/code-reviewer.md

Result:

• Creates agents/code-reviewer.md with template
• Frontmatter description: "Reviews code for quality, security, and best practices"
• Ready to customize with specific review criteria

Example 2: From Marketplace Root with --plugin

Context: Currently in /path/to/marketplace/ (marketplace root)

Input:

/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices" --plugin=plugin-development

Process:

1. Detects .claude-plugin/marketplace.json in current directory
2. Extracts --plugin=plugin-development from arguments
3. Validates plugins/plugin-development/.claude-plugin/plugin.json exists
4. Uses plugins/plugin-development/ as target
5. Creates plugins/plugin-development/agents/code-reviewer.md

Result:

• Creates plugins/plugin-development/agents/code-reviewer.md
• Agent added to plugin-development plugin

Example 3: From Marketplace Root without --plugin

Context: Currently in /path/to/marketplace/ (marketplace root)

Input:

/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices"

Process:

1. Detects .claude-plugin/marketplace.json in current directory
2. No --plugin argument provided
3. Reads marketplace.json and discovers available plugins:
   • hello-world - A simple example plugin
   • plugin-development - Assist with Claude Code plugin development
4. Prompts user: "Which plugin should I add the agent to?"

   1. hello-world - A simple example plugin demonstrating basic Claude Code plugin functionality
   2. plugin-development - Assist with Claude Code plugin development: scaffold, validate, review, and team-ready distribution
   

5. User selects option 2
6. Uses plugins/plugin-development/ as target
7. Creates plugins/plugin-development/agents/code-reviewer.md

Result:

• Creates plugins/plugin-development/agents/code-reviewer.md
• Agent added to selected plugin

Agent Frontmatter

Required Fields

---
description: Third-person description of what this agent does
---

Optional Fields

---
description: Agent description
capabilities: ["capability-1", "capability-2"]    # List of what it can do
---

For complete details on agents, see:

• Subagents documentation
• Plugin agents reference

Error Handling

Not in Plugin or Marketplace Directory

Error: "Not in a plugin or marketplace directory."

Solution: Navigate to either:

• A plugin directory (containing .claude-plugin/plugin.json), OR
• A marketplace root (containing .claude-plugin/marketplace.json)

Plugin Not Found

Error: "Plugin 'my-plugin' not found. Available plugins: hello-world, plugin-development"

Solution:

• Check plugin name spelling
• Use --plugin=<correct-name> with one of the available plugins
• Or navigate to the plugin directory directly

Invalid Agent Name

Error: "Agent name must be in kebab-case format (lowercase with hyphens)"

Solution: Use kebab-case format:

• ✅ Good: code-reviewer, security-auditor, api-generator
• ❌ Bad: CodeReviewer, code_reviewer, code reviewer

Missing Description

Error: "Description is required"

Solution: Provide description in quotes:

/plugin-development:add-agent code-reviewer "Reviews code for quality, security, and best practices"

When to Use Agents vs. Commands vs. Skills

Use an Agent when:

• Task requires deep, multi-file analysis
• Need separate context window (complex reasoning)
• Want detailed, structured report back
• Task has multiple steps that benefit from isolation

Use a Command when:

• Task is explicit, one-time action
• User needs to trigger on demand
• Task is straightforward with clear inputs/outputs

Use a Skill when:

• Want ambient, automatic activation
• Need persistent guidance throughout session
• Task benefits from progressive disclosure
• Should trigger based on context clues

Agent Design Best Practices

1. Focused Scope

✅ Good (focused):

# Code Security Auditor

Specializes in security analysis:
- SQL injection vulnerabilities
- XSS vulnerabilities
- Authentication issues

❌ Bad (too broad):

# General Code Helper

Does everything related to code.

2. Clear Capabilities

List 2-5 specific capabilities:

capabilities: [
  "security-vulnerability-detection",
  "authentication-analysis",
  "dependency-audit"
]

3. Structured Output

Define consistent report format:

## Critical (P0)
- [List critical issues]

## High Priority (P1)
- [List high priority issues]

## Suggestions
- [List improvements]

4. Tool Restrictions

Agents typically don't modify files:

## Tool Access

- Read, Grep, Glob: For analysis
- No Write/Edit: Agent proposes, main conversation executes

Agent Workflow Template

All agents should follow a consistent structure:

1. **Understand Context**: Read relevant files
2. **Analyze**: Apply domain expertise
3. **Identify Issues**: Find problems/opportunities
4. **Prioritize**: Rank by severity/importance
5. **Recommend**: Provide actionable guidance
6. **Report**: Return structured findings

Common Agent Patterns

Auditor Pattern

For review/analysis agents:

• Reads multiple files
• Checks against standards/criteria
• Reports issues by severity
• Provides specific fix recommendations

Generator Pattern

For design/planning agents:

• Analyzes requirements
• Proposes architecture/approach
• Provides implementation steps
• Returns detailed plan

Refactoring Pattern

For code improvement agents:

• Analyzes existing code
• Identifies improvement opportunities
• Proposes refactoring steps
• Estimates impact/effort

Invocation Methods

Direct Invocation

User explicitly calls the agent:

/agents code-reviewer

Via Main Conversation

Claude uses Task tool:

Let me use the code-reviewer agent to analyze this...

From Skill

Skill escalates to agent for deep analysis:

For comprehensive review, delegate to the code-reviewer agent.

Best Practices

1. Single responsibility: One clear purpose
2. Structured output: Consistent report format
3. No side effects: Read-only, propose changes
4. Clear scope: 2-5 capabilities max
5. Fast feedback: Aim for < 30 seconds runtime
6. Actionable results: Specific, implementable recommendations

Common Mistakes to Avoid

❌ Too broad scope

capabilities: ["everything", "all-tasks", "general-help"]

✅ Focused capabilities

capabilities: ["security-audit", "vulnerability-scan", "compliance-check"]

❌ Vague instructions

Analyze the code and find problems.

✅ Specific workflow

1. Read all .py files in src/
2. Check for SQL injection patterns
3. Verify authentication usage
4. Report findings by severity

Validation Checklist

After creating an agent:

□ Agent file created in agents/ directory
□ Frontmatter includes description
□ Capabilities listed (2-5 items)
□ Clear workflow defined
□ Output format specified
□ Agent name is kebab-case
□ plugin.json has agents field
□ Purpose is focused and specific