Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add testdouble/han/plugin install han-plugin-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/testdouble/han/agent-builder)<a href="https://agentmods.dev/skills/testdouble/han/agent-builder"><img src="https://agentmods.dev/badge/skills/testdouble/han/agent-builder/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/testdouble/han/agent-builder"><img src="https://agentmods.dev/badge/skills/testdouble/han/agent-builder.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00130 | $0.03322 |
| Opus 5.5 | $0.00052 | $0.01329 |
| Sonnet 5.5 | $0.00026 | $0.00664 |
| Haiku 4.5 | $0.00013 | $0.00332 |
Grade A, and why
agent-builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 201 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Project Context
- personal config directory: !
bash "${CLAUDE_PLUGIN_ROOT}/scripts/han-config-dir.sh" 2>/dev/null || echo "$HOME/.claude" - project .han/config.md: !
cat .han/config.md 2>/dev/null || echo ""
As your first action, use the Read tool on .han/config.md inside the personal config directory path above. A read
that returns no file is no personal configuration: continue silently. When that file or the project .han/config.md
probe supplies content, apply it per config-rule.md, which governs precedence
between the two files, relative-path resolution, and what to do with a file that reads but cannot be used.
Guidance Location
The authoritative agent-authoring guidance ships in this plugin. Read the specific document a decision needs, when that decision is on the table — never read them all up front, because that defeats progressive disclosure and burns context on guidance the current agent does not touch.
- Plugin-building guidance root:
${CLAUDE_PLUGIN_ROOT}/skills/guidance/references/ - Agent-specific guidance:
${CLAUDE_PLUGIN_ROOT}/skills/guidance/references/agent-building-guidelines/
Map from decision to governing document (read just-in-time):
| Decision on the table | Read |
|---|---|
| Agent vs. skill vs. hook; one role (generate or evaluate) | plugin-entity-taxonomy.md, agent-building-guidelines/agent-domain-focus.md |
| Domain focus, vocabulary, role identity, anti-patterns | agent-building-guidelines/agent-domain-focus.md |
The description field (four components, boundaries, length) |
agent-building-guidelines/agent-description-length.md, skill-building-guidance/skill-description-frontmatter.md |
Model tier (opus / sonnet / haiku / inherit) |
agent-building-guidelines/agent-model-selection.md, specialization-and-model-selection.md |
| Self-containment — no references, scripts, or context injection | agent-building-guidelines/agent-external-files.md |
| Which frontmatter fields are valid (and which plugins ignore) | agent-building-guidelines/agent-external-files.md |
| Degraded environments (no git, missing tools) | agent-building-guidelines/graceful-degradation.md |
| Whether this agent is justified at all; how it gets dispatched | agent-building-guidelines/multi-agent-economics.md, skill-building-guidance/agent-dispatch-namespacing.md |
| New plugin needed (plugin.json, marketplace.json) | claude-marketplace-and-plugin-configuration/ and templates/ |
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.
- 1mo ago First seen · 201 lines · 130 tokens per session scan A 4d3877bb5f72
agent-builder is a skill published in the GitHub repository testdouble/han (323 stars, last pushed 9d ago), licensed MIT. It adds 130 tokens to every session and 3,322 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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