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 alessiomarcone/agent-fieldbook --skill subagentgit clone --depth 1 https://github.com/alessiomarcone/agent-fieldbookWrote 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/alessiomarcone/agent-fieldbook/subagent)<a href="https://agentmods.dev/skills/alessiomarcone/agent-fieldbook/subagent"><img src="https://agentmods.dev/badge/skills/alessiomarcone/agent-fieldbook/subagent/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/alessiomarcone/agent-fieldbook/subagent"><img src="https://agentmods.dev/badge/skills/alessiomarcone/agent-fieldbook/subagent.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 | $0.00076 | $0.00558 |
| Opus 5 | $0.00038 | $0.00279 |
| Sonnet 5 | $0.00015 | $0.00112 |
| Haiku 4.5 | $0.00008 | $0.00056 |
Grade A, and why
subagent 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 8d 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 — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Subagent
Design the smallest delegated unit that can return a decision-ready handoff.
References
Resolve the product first, then read only its branch:
- Claude Code:
references/claude-code-subagents.md. - Anthropic Managed Agents: also read
references/managed-agents.md. - Codex:
references/codex-subagents.md.
Never transfer fields, commands, models, tools, or permission semantics between branches. For a cross-product migration, read both the source and target official references, map intent and constraints, and never map fields by analogy.
Decision gate
Use a subagent only when at least one is true:
- independent work can proceed in parallel;
- a separate context prevents noise or context pollution;
- a specialist needs a different model, tool, or sandbox boundary;
- the parent needs a compact result rather than the full exploration.
Otherwise return only Verdict and Simpler route, then stop.
Procedure
- Identify the exact surface and current supported configuration format.
- Define objective, inputs, exclusions, allowed tools, authority, deliverable, and success test.
- Default investigations to read-only. Require explicit authority for edits, external messages, publication, or destructive effects.
- State what context the child receives, must discover, and must not assume.
- Prefer read-heavy parallelism; coordinate agents that share writable state.
- Require a handoff with evidence, changes, unresolved risks, and a concise conclusion.
- When implementation is requested, verify time-sensitive configuration against current official documentation and validate the file.
Output contract
When the verdict is yes, return:
- Verdict — why delegation is warranted.
- Contract — objective, inputs, exclusions, tools, and authority.
- Prompt/configuration — ready to use for the selected product.
- Handoff — exact required return shape.
- Tests — normal, boundary, and failure case.
Boundaries
- Do not invent configuration fields or availability.
- Do not activate for an open comparison such as “custom agent or skill?”; route mechanism comparisons to
navigate. - Do not accept “research this” without a decision-ready deliverable.
- Do not permit silent external side effects.
- Answer in the user's language.
What ships with it
4 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.
- 8d ago First seen · 60 lines · 76 tokens per session scan A 00853e9af6c6
subagent is a skill published in the GitHub repository alessiomarcone/agent-fieldbook (5 stars, last pushed yesterday), licensed MIT. It adds 76 tokens to every session and 558 once invoked, about $0.0004 per session on Opus 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 2026-08-31.
Other skills, from other repositories
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create-agent-skills
Expert guidance for creating, writing, building, and refining Claude Code Skills. Use when working with SKILL.md files, authoring new skills, improving existing skills, or understanding skill structure and best practices.
customer-support-expert
Build comprehensive customer support systems including ticketing, knowledge management, SLA tracking, and customer satisfaction analytics. Use when the user mentions helpdesk or service desk, ticketing, SLA targets, knowledge bases, escalation workflows, CSAT/NPS, or customer success operations.
software-in-worten
Übersetzt zwischen Benutzeroberfläche und Text — in beide Richtungen. Aus einer beschriebenen Oberfläche wird ein Skill; aus einem Skill wird eine Oberfläche. Nutzen, wenn eine Anwendung entworfen wird und der Ablauf noch unklar ist, wenn ein bestehendes Werkzeug als Skill verfügbar gemacht werden soll, wenn…
decision-board
Render an interactive HTML board for the user to pick among multiple comparable options side-by-side at once — engineering trade-offs, copy audits, action-item triage, architecture decisions, policy calls. Returns the picks (and optional hold/note flags) as a JSON file the agent can apply.
instruction-eval
Change one condition an agent runs under (instruction text, the reference material instructions point at, MCP tools and permissions, hooks, skill files), then run the same prompts before and after, several times each, to see what actually changes. Produces an HTML report showing both arms' answers side by side. Use…