This skill should be used when the user asks to "create a subagent", "validate a subagent", "generate subagent schema", "check subagent configuration", "write subagent specification", or mentions subagent development, validation, or protocol documentation for Claude Code.
SkillScore100Maintained
Automatic
◆AI Engineer pack
Last verified 8/19/2026
What it changes
Passed 22 of 22 test cases with the skill, and 12 of 22 without it.
Without skill55%
With skill100%
Checks it passed that the model alone missed
The response designates opus as the model alias.
The response designates inherit as the model value.
The response identifies 10 characters as the minimum length.
and 13 more in the full report
10 fixed12 passed either way0 still failing0 broke
Pass-rate lift
+45 pp
Tokens
+130%
Agent turns
0%
Response time
-40%
Model gemini-3.6-flashMeasured 8/19/2026v122 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 10 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 10
Prompt
What are the minimum and maximum character length constraints enforced by schema validation on a Claude Code subagent's frontmatter `description` field?
What was checked, without and with the skill
Checked
Without skill
With skill
The response identifies 10 characters as the minimum length.
Missed
Passed
The response identifies 2000 characters as the maximum length.
Missed
Passed
case-12 · gemini-3.6-flash · 8/19/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md412 linessingle file
Claude Code Subagent Development
Comprehensive guidance for creating, validating, and documenting Claude Code subagents with schemas and protocol specifications.
Purpose
This skill provides structured workflows for developing production-ready Claude Code subagents. Use when creating new subagents, validating existing configurations, generating JSON schemas for validation, or writing technical specifications for subagent protocols.
When to Use
This skill should be used when:
Creating new subagent configurations
Validating subagent YAML frontmatter and structure
Generating JSON schemas for subagent validation
Writing protocol specifications and technical documentation
Reviewing subagent configurations for best practices
Debugging subagent loading or invocation issues
Core Concepts
Subagent Structure
Subagents are Markdown files with YAML frontmatter:
---
name: subagent-identifier
description: When and how to use this subagent
tools: Tool1, Tool2
model: sonnet
permissionMode: default
skills: skill1, skill2
---
System prompt content in Markdown format.
Required Fields
name: Lowercase identifier with hyphens (pattern: ^[a-z0-9-]+$)
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