agent-builder

name	agent-builder
description	Creates Claude Code agent files (.claude/agents/*.md) with YAML frontmatter, tool permissions, and system prompts. Use when building new agents, configuring agent frontmatter, writing agent system prompts, or setting agent tool permissions.

[H1][AGENT-BUILDER]

Dictum: Structured frontmatter and scoped tools enable discoverable agents.

Specialized execution contexts for Claude Code subagent delegation. Frontmatter controls discovery and capabilities; markdown body encodes behavior.

Location: .claude/agents/ (project) or ~/.claude/agents/ (user). Higher priority wins: CLI flag > project > user > plugin.

Tasks:

1. Read frontmatter.md — Complete schema (11 fields), triggers, syntax.
2. Read prompt.md — Structure patterns, constraint markers.
3. Read workflow.md — 5-phase creation process.
4. (prose) Load style-standards skill — Voice, formatting, constraints.
5. Execute per workflow — UNDERSTAND, ACQUIRE, RESEARCH, AUTHOR, VALIDATE.
6. Validate — Quality gate; see §VALIDATION.

References:

Domain	File
Workflow	workflow.md
Frontmatter	frontmatter.md
Prompt	prompt.md
Validation	validation.md
Template	agent.template.md

---

[1][FRONTMATTER]

Dictum: Metadata enables discovery before load.

---
name: agent-name
description: >-
  Capability statement. Use when scenario-1, scenario-2, or scenario-3.
tools: Read, Glob, Grep
model: sonnet
skills:
  - style-standards
memory: user
---

[INDEX]	[FIELD]	[TYPE]	[REQ]	[CONSTRAINT]
[1]	name	string	Yes	Kebab-case, max 64 chars, match filename
[2]	description	string	Yes	Third person, active voice, "Use when" clause
[3]	tools	list	No	Comma-separated allowlist; omit = inherit all
[4]	disallowedTools	list	No	Denylist; removed from inherited/allowed tools
[5]	model	enum	No	haiku, sonnet, opus, inherit
[6]	permissionMode	enum	No	default, acceptEdits, delegate, dontAsk, bypassPermissions, plan
[7]	maxTurns	number	No	Maximum agentic turns before subagent stops
[8]	skills	list	No	Full skill content preloaded at startup
[9]	mcpServers	object	No	MCP servers available to this subagent
[10]	hooks	object	No	Scoped lifecycle hooks (all 14 events supported)
[11]	memory	enum

[IMPORTANT] Agent background color set interactively via /agents UI — not frontmatter field.

---

[2][DISCOVERY]

Dictum: Description quality determines invocation accuracy.

Reasoning matches description directly — no embeddings, no keyword matching.

[INDEX]	[PATTERN]	[EXAMPLE]	[MECHANISM]
[1]	"Use when" clause	Use when building MCP servers	Direct activation signal
[2]	Proactive trigger	Use proactively after code changes	Encourages auto-invocation
[3]	Imperative emphasis	MUST BE USED before committing	Strong delegation signal
[4]	Enumerated list	(1) creating, (2) modifying	Parallel pattern matching
[5]	Technology embed	Python (FastMCP) or TypeScript	Framework-specific match

[CRITICAL]:

• [NEVER] Hedging words: might, could, should, probably.
• [ALWAYS] Include "Use when" clause — 3+ trigger scenarios.
• [ALWAYS] Third person, active voice, present tense.

---

[3][TOOLS]

Dictum: Tool declarations scope permissions.

[INDEX]	[PATTERN]	[TOOLS]	[USE_CASE]
[1]	Read-only	Read, Glob, Grep	Analysis, review
[2]	Write-capable	Read, Edit, Write, Glob, Bash	Implementation
[3]	Orchestration	Task(worker, researcher), Read	Agent dispatch
[4]	Full access	(omit field)	Inherits all tools

Task restriction: Task(agent_type) limits spawnable subagent types (main thread only). Denylist: disallowedTools: Write, Edit removes tools from inherited or allowed set.

---

[4][MODELS]

Dictum: Model selection balances capability against latency and cost.

[INDEX]	[MODEL]	[STRENGTH]	[LATENCY]	[COST]
[1]	opus	Complex reasoning	High	High
[2]	sonnet	Balanced performance	Medium	Medium
[3]	haiku	Fast, simple tasks	Low	Low
[4]	inherit	Match main conversation	Session	Session

---

[5][SYSTEM_PROMPT]

Dictum: Structured prompts constrain execution.

Markdown body follows frontmatter. Body encodes agent behavior; structure determines effectiveness. Subagents receive only this system prompt (plus environment details), NOT full Claude Code system prompt.

---

[6][NAMING]

Dictum: Naming conventions enable discovery.

[INDEX]	[PATTERN]	[EXAMPLE]	[USE_CASE]
[1]	Role-based	code-reviewer	Specialized function
[2]	Action-based	generating-commits	Gerund form preferred
[3]	Domain-specific	react-specialist	Technology expertise

[CRITICAL]:

• [NEVER] Generic names: helper, processor, agent.
• [ALWAYS] Kebab-case — lowercase, hyphens only. Filename matches name field.

---

[7][VALIDATION]

Dictum: Validation gates prevent incomplete artifacts.

[VERIFY] Completion:

• Workflow: All 5 phases executed (UNDERSTAND → VALIDATE).
• Frontmatter: Valid YAML, description with "Use when" clause.
• Tools: Matches type gate (readonly|write|orchestrator|full).
• Prompt: Role line + H2 sections + constraint markers.
• Quality: Kebab-case naming, filename matches name field.

[REFERENCE] Operational checklist: →validation.md.