Subagent
Decides whether selected delegated work needs agents and designs a strict, product-correct subagent contract with isolated context, bounded tools, authority, deliverables, and tests. Use when the user asks to create, configure, delegate to, or troubleshoot Claude or Codex subagents, parallel agents, custom agents, or managed-agent workflows; not for open mechanism comparisons.
Install
$ agentstack add skill-alessiomarcone-agent-fieldbook-subagent ✓ scanned · ✓ verified — works with Claude Code, Cursor, and more.
Security review
✓ PassedNo issues found. Passed automated security review. · v0.1.0 How review works →
- ✓ Prompt-injection patterns
- ✓ Secret / credential exfiltration
- ✓ Dangerous shell & filesystem operations
- ✓ Untrusted network calls
- ✓ Known-malicious package signatures
What it can access
- ✓ Network access No
- ✓ Filesystem access No
- ✓ Shell / process execution No
- ✓ Environment & secrets No
- ✓ Dynamic code execution No
From automated source analysis of v0.1.0. “Used” means the capability is present in the source — more access means more to trust, not that it’s unsafe.
About
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.
Source & license
This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.
- Author: alessiomarcone
- Source: alessiomarcone/agent-fieldbook
- License: MIT
Install and usage instructions live in the source repository linked above.
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Versions
- v0.1.0 Imported from the upstream source.