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 cambridgetcg/agenttool --skill nen-dependency-perimetergit clone --depth 1 https://github.com/cambridgetcg/agenttoolWrote 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/cambridgetcg/agenttool/nen-dependency-perimeter)<a href="https://agentmods.dev/skills/cambridgetcg/agenttool/nen-dependency-perimeter"><img src="https://agentmods.dev/badge/skills/cambridgetcg/agenttool/nen-dependency-perimeter/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/cambridgetcg/agenttool/nen-dependency-perimeter"><img src="https://agentmods.dev/badge/skills/cambridgetcg/agenttool/nen-dependency-perimeter.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 | $0.00070 | $0.00627 |
| Opus 5 | $0.00035 | $0.00313 |
| Sonnet 5 | $0.00014 | $0.00125 |
| Haiku 4.5 | $0.00007 | $0.00063 |
Grade A, and why
nen-dependency-perimeter 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 — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Dependency Perimeter · 円
Extend a finite field around the exact task. Observe what enters, leaves, and depends on that field before changing it.
Set the field
Declare:
- Center: the requested behavior, artifact, symptom, or decision.
- Radius: paths, packages, services, actors, environments, and time horizon included in the scan.
- Resolution: broad inventory or deep edge tracing.
- Exit: the evidence needed before an already-authorized implementation may begin.
Larger fields lower resolution and cost more attention. Prefer the smallest radius that can reveal the real blast surface.
Expand read-only
- Read the closest instructions, manifests, status, and architecture maps.
- Inventory the center with fast native discovery tools.
- Trace inbound edges: callers, imports, routes, jobs, configuration, schemas, users, and operational entry points.
- Trace outbound edges: dependencies, storage, network calls, generated artifacts, side effects, and downstream consumers.
- Locate existing tests, fixtures, observability, owners, and rollback paths.
- Sample just outside the chosen radius for missed aliases, indirect callers, or duplicated implementations.
- Mark every edge as observed, inferred, or unknown.
Do not read secret-bearing files merely because they are nearby. Inventory the boundary or schema without exposing values.
Draw the perimeter
Return the smallest useful map:
Center:
Inside:
Inbound:
Outbound:
Protected boundaries:
Unknown outside field:
Verification targets:
Next move:
Use a table, tree, or flow only when it makes three or more relationships materially easier to understand.
Collapse or refresh
If the task already authorizes mutation, begin it only after the field explains the likely blast radius. Otherwise, return the map and proposed next move without mutating. Refresh changed edges after implementation; do not rerun a full scan when a targeted perimeter check is enough.
Vow
What ships with it
1 file 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 · 81 lines · 70 tokens per session scan A c4c2cad4fca6
nen-dependency-perimeter is a skill published in the GitHub repository cambridgetcg/agenttool (0 stars, last pushed today), licensed Apache-2.0. It adds 70 tokens to every session and 627 once invoked, about $0.0003 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.
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