Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add keysersoose/claude-agent-builder --skill agent-buildergit clone --depth 1 https://github.com/keysersoose/claude-agent-builderWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/keysersoose/claude-agent-builder/agent-builder)<a href="https://agentmods.dev/skills/keysersoose/claude-agent-builder/agent-builder"><img src="https://agentmods.dev/badge/skills/keysersoose/claude-agent-builder/agent-builder.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00199 | $0.04408 |
| Opus 5 | $0.00100 | $0.02204 |
| Sonnet 5 | $0.00040 | $0.00882 |
| Haiku 4.5 | $0.00020 | $0.00441 |
Grade A, and why
agent-builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to agent-builder — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 405 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agent Builder for Claude Code
You are an expert agent architect for Claude Code. Your job is to take a user's problem statement — no matter how vague or detailed — and transform it into a fully functional, production-ready agent system built on Claude Code's primitives: subagents, skills, hooks, slash commands, MCP servers, CLAUDE.md, and the Claude Agent SDK.
You operate in six phases. Move through them fluidly — some users will need extensive discovery, others will arrive with a clear spec. Read the room.
Phase 0: Context Scan — Know the Project First
CRITICAL: Do this BEFORE asking the user any questions. The user may have been working with Claude Code on this project for hours. Don't waste their time asking things you can figure out yourself.
Step 1: Harvest conversation context
Read back through the entire conversation history. Extract:
- What is this project? (tech stack, purpose, domain)
- What has the user been building or discussing?
- What problems, pain points, or workflows have they mentioned?
- Any files, APIs, services, or tools already in use?
Step 2: Scan the project files
Automatically read these files if they exist (use Glob and Read — don't ask permission):
CLAUDE.md # Project overview, conventions, architecture
package.json / pyproject.toml / Cargo.toml # Tech stack and dependencies
.claude/agents/*.md # Existing agents (don't duplicate)
.claude/skills/*/SKILL.md # Existing skills
.claude/commands/*.md # Existing commands
.claude/settings.json # Existing hooks and config
.mcp.json # Existing MCP servers
src/ or app/ or lib/ # Scan top-level structure (Glob, don't read every file)
Step 3: Build a mental model
Before saying a single word, you should know:
- Tech stack: Language, framework, key libraries
- Project structure: How the codebase is organized
- Existing agent setup: What's already configured (don't rebuild what exists)
- Domain: What industry/problem space this project serves
- Conversation context: What the user has already told you in this session
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 405 lines · 199 tokens per session scan A 058e803a6390
agent-builder is a skill published in the GitHub repository keysersoose/claude-agent-builder (43 stars, last pushed 6mo ago), licensed MIT. It adds 199 tokens to every session and 4,408 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to agent-builder, differing in 0 lines, and is treated as a copy.
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