JaviMontano/skills/agent-creator

Agent Creator

Create custom Claude Code agents — autonomous subprocesses with isolated context, specific tools, and tailored system prompts. [EXPLICIT]

Assumptions & Limits

• Assumes the task is genuinely better served by a subagent than inline instructions (not everything needs an agent)
• Limit: Agents inherit parent permissions but NOT parent context — they start fresh, so system prompts must be self-sufficient
• Limit: Agent names must not collide with built-ins: Explore, Plan, general-purpose
• Trade-off: More tools = more capable but slower and riskier; fewer tools = faster but may fail on edge cases

When NOT to create an agent

| Situation | Better alternative | |---|---| | One-off task instruction | CLAUDE.md rule | | Reusable multi-step workflow | Skill with context: fork | | Simple output format change | Output style | | Always-run automation | Hook |

Usage

/agent-creator security-reviewer "Reviews code for OWASP vulnerabilities"
/agent-creator test-writer                    # interview mode

Parse $1 as agent name (kebab-case), $2 as description. If $2 absent, ask: [EXPLICIT]

1. What should this agent analyze or produce?
2. Should it modify files or only read/report?
3. What complexity level? (haiku=simple, sonnet=balanced, opus=complex reasoning)

Before Creating

1. Read official spec: Read ~/.claude/plugins/marketplaces/claude-plugins-official/plugins/plugin-dev/skills/agent-development/SKILL.md
2. Check existing: Glob .claude/agents/*.md and Glob ~/.claude/agents/*.md
3. Verify no name collision with built-in agents

Agent File Anatomy

File: .claude/agents/{name}.md (project) or ~/.claude/agents/{name}.md (global) [EXPLICIT]

---
name: agent-creator
description: "{When Claude should spawn this agent — be specific about trigger conditions}"
model: "{haiku|sonnet|opus}"
color: "{hex, e.g. #4CAF50}"
tools: ["{minimum tool set}"]
---

# {Agent Name}

You are {Name}, a specialized agent that {concrete role}. [EXPLICIT]

## Your Task

{Specific, bounded description. Include: what to analyze, what to produce, what format.}

## Process

{Numbered steps the agent follows. Each step = concrete action.}

## Output Format

{Exact structure of the expected output. Use code blocks.}

## Constraints

- {Hard boundaries: what NOT to do}
- {Escalation triggers: when to report back instead of acting}

## Reasoning Discipline

Apply structured thinking to every analysis and recommendation. [EXPLICIT]

1. **Decompose** — Break complex problems into max 5 sub-problems before solving
2. **Evidence-check** — Tag every claim with confidence `[CONFIANZA: alta|media|baja]` and evidence source
3. **Bias scan** — Before finalizing, check for anchoring, confirmation, and availability bias
4. **Structure-first** — For planning outputs, build bullet skeleton before expanding prose
5. **Escalate** — When confidence is low (`baja`), flag uncertainty and present alternatives rather than guessing

## Quality Bar

- {Minimum standard each output must meet}

Frontmatter Decision Matrix

| Field | Required | Decision Logic | |---|---|---| | name | Yes | Display name for UI/logs. Title case. | | description | Yes | Must state WHEN to spawn, not just WHAT it does. Claude reads this to decide auto-invocation. | | model | Recommended | haiku: pattern matching, formatting, simple checks. sonnet: analysis, review, generation. opus: architecture, security audit, complex reasoning. | | color | Optional | Hex for terminal UI. Use consistent palette across related agents. | | tools | Recommended | Omit = inherit all parent tools (risky). Empty [] = advisory only (can't read files). Explicit list = principle of least privilege. |

Tool Restriction Patterns

| Pattern | Tools | Use Case | Risk Level | |---|---|---|---| | Advisory | [] | Planning, brainstorming | None | | Read-only | ["Read", "Glob", "Grep"] | Review, analysis, audit | Low | | Read-write | ["Read", "Write", "Edit", "Glob", "Grep"] | Generation, refactoring | Medium | | Full access | ["Read", "Write", "Edit", "Bash", "Glob", "Grep"] | Build, deploy, test | High |

Default to read-only unless the agent must create/modify artifacts.

System Prompt Design Principles

| Principle | Rationale | Anti-pattern | |---|---|---| | Self-sufficient context | Agent has no parent history | Referencing "the file we discussed" | | Bounded scope | Prevents scope creep | "Handle anything related to X" | | Explicit output format | Enables downstream consumption | "Summarize your findings" | | Concrete process steps | Reproducible behavior | "Use your best judgment" | | Negative constraints | Prevents common mistakes | No constraints section |

Edge Cases

• Agent needs project-specific context: Use !command in the skill that spawns it to inject dynamic state
• Agent spawns too often: Narrow the description trigger conditions; add "Only spawn when X AND Y"
• Agent output too verbose: Add token/line limits in system prompt ("Max 50 lines")
• Multiple agents for related tasks: Create an agent "team" with clear ownership boundaries per file/module

Example: Production-Quality Agent

---
name: agent-creator
description: Audit package dependencies for security vulnerabilities, license compliance, and update availability. Spawn when user asks about dependencies, security, or runs npm audit. [EXPLICIT]
model: sonnet
color: "#FF6B35"
tools: ["Read", "Glob", "Grep", "Bash"]
---

# Dependency Auditor

You are Dependency Auditor. You analyze project dependencies for security, licensing, and freshness. [EXPLICIT]

## Your Task

Audit all dependency files (package.json, requirements.txt, Cargo.toml, go.mod) in the project and produce a structured report. [EXPLICIT]

## Process

1. Find dependency files: `Glob **/package.json **/requirements.txt **/Cargo.toml **/go.mod`
2. For each file, read and catalog: name, current version, type (dev/prod)
3. Run security check: `npm audit --json` / `pip audit --format json` / equivalent
4. Check licenses: identify copyleft (GPL) vs permissive (MIT, Apache)
5. Identify outdated: compare current vs latest via registry

## Output Format

| Package | Current | Latest | Severity | License | Action |
|---|---|---|---|---|---|
| lodash | 4.17.20 | 4.17.21 | High (CVE-2021-23337) | MIT | Update |

## Constraints

- Read-only analysis: never modify dependency files
- Report findings; do not auto-fix
- If `npm audit` fails, report the error and continue with manual analysis
- Max 100 dependencies per report; for larger projects, split by directory

Validation Gate

• [ ] File is valid Markdown with YAML frontmatter
• [ ] name and description present and non-empty
• [ ] description states trigger conditions (WHEN), not just capabilities (WHAT)
• [ ] tools explicitly listed (not relying on inheritance)
• [ ] System prompt is self-sufficient (no references to parent context)
• [ ] Output format is explicitly defined (code block or table)
• [ ] Constraints section includes at least 1 "do NOT" boundary
• [ ] No naming collision with Explore, Plan, general-purpose
• [ ] Model selection justified by task complexity
• [ ] Reasoning Discipline section present (LIGHT tier for standard agents)
• [ ] File saved to correct scope (project vs global)

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Author: Javier Montano | Last updated: March 18, 2026