Subagent Implementation
Technical reference for implementing subagents. Use when asked about frontmatter fields, system prompt structure, or subagent file format. Provides essential specs with references for details.
What this skill does
## File Structure
Subagent files are Markdown with YAML frontmatter:
```markdown
---
name: agent-name
description: When to use this agent...
model: inherit
color: blue
tools: ["Read", "Grep"]
---
You are [agent role]...
**Responsibilities:**
1. [Task 1]
2. [Task 2]
```
**Location:** `.claude/agents/` or `.claude-plugin/agents/`
**Naming:** kebab-case, 3-50 chars (e.g., `code-reviewer`)
## Frontmatter Fields
### Required Fields
| Field | Format | Example |
|-------|--------|---------|
| `name` | kebab-case, 3-50 chars | `code-reviewer` |
| `description` | Text with 2-4 examples | See below |
| `model` | `inherit`/`haiku`/`sonnet`/`opus` | `inherit` |
| `color` | `blue`/`cyan`/`green`/`yellow`/`magenta`/`red` | `blue` |
### Description Format
Include 2-4 `<example>` blocks:
```yaml
description: |
Use when reviewing code for quality. Examples:
<example>
Context: User wrote new code
user: "Review this"
assistant: "I'll use the code-reviewer"
<commentary>Code review is core function</commentary>
</example>
```
### Optional Fields
| Field | Purpose | Example |
|-------|---------|---------|
| `tools` | Restrict tool access | `["Read", "Grep", "Glob"]` |
| `permissionMode` | Permission handling | `acceptEdits` |
| `skills` | Preload skills | `["api-conventions"]` |
**Permission modes:** `default`, `acceptEdits`, `dontAsk`, `bypassPermissions`, `plan`
See `references/frontmatter-reference.md` for complete field documentation.
## System Prompt Template
```markdown
You are a [role] specializing in [domain].
**Responsibilities:**
1. [Primary task]
2. [Secondary task]
**Process:**
1. [Step 1]
2. [Step 2]
3. [Verification]
**Output Format:**
[Specify exact output structure]
**Edge Cases:**
- [Case 1]: [How to handle]
```
### Writing Guidelines
**DO:**
- Use second person ("You are...")
- Be specific and concrete
- Define output format clearly
- Keep under 10,000 characters
**DON'T:**
- Use first person ("I am...")
- Be vague
- Skip process steps
- Exceed 10k chars
See `references/system-prompt-patterns.md` for detailed templates.
## Quick Checklists
### Frontmatter
- [ ] name: 3-50 chars, kebab-case
- [ ] description: 2-4 examples
- [ ] model: valid option
- [ ] color: valid option
- [ ] tools: (optional) minimum needed
### System Prompt
- [ ] Clear role statement
- [ ] Numbered responsibilities
- [ ] Step-by-step process
- [ ] Explicit output format
- [ ] Edge cases addressed
- [ ] Under 10k chars
## Testing
1. **Syntax:** Valid YAML frontmatter
2. **Trigger:** Questions activate agent
3. **Behavior:** Matches description
4. **Output:** Follows format
## References
For complete documentation:
- `references/frontmatter-reference.md` - All fields with examples
- `references/system-prompt-patterns.md` - Detailed templates
- `examples/complete-analyzer-example.md` - Working example
For distribution via marketplaces, see the Anthropic docs on [Plugin Marketplaces](https://code.claude.com/docs/en/plugin-marketplaces).
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