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 agentmods add skills/howells/arc/detailnpx skills add howells/arc --skill detailgit clone --depth 1 https://github.com/howells/arcWhat 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 | $0.00034 | $0.01807 |
| Opus 5 | $0.00017 | $0.00903 |
| Sonnet 5 | $0.00007 | $0.00361 |
| Haiku 4.5 | $0.00003 | $0.00181 |
Grade A, and why
detail 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 2d 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 — 191 lines — stays where its author put it; the contents beside it link to each section on GitHub.
<tool_restrictions>
EnterPlanMode and ExitPlanMode are banned. This skill is Arc's plan-writing process.
</tool_restrictions>
<arc_runtime>
Requires the full Arc bundle. Arc-owned paths (agents/, references/, disciplines/, templates/, scripts/, rules/, skills/) resolve from the plugin root — the directory containing agents/ and skills/. Everything else is the user's repository.
</arc_runtime>
<required_reading> Read before planning:
references/implementation-assurance.md— posture, ownership, review, verification ladderreferences/task-granularity.md— normative XML and slice cohesionreferences/testing-patterns.md— seams and work-kind evidencereferences/checkpoint-patterns.md— genuine human gatesreferences/arc-paths.md— artifact locationsreferences/plan-lifecycle.md— plan header, drift, status, decision log </required_reading>
1. Load the scope input
detail accepts either:
- a feature spec from
implement, preferringdocs/arc/specs/*-spec.md; - a vetted finding from
improve, including evidence, impact, fix sketch, and out-of-scope candidates; or - a direct scoped request forwarded by
implementwith no spec behind it. Elicit the missing scope through questions (perreferences/question-loops.md) rather than substituting a stale spec. If no user is available, resolve what you can from the request's own constraints and repo evidence, record every unanswered question in the Decision log, and mark the plan unconfirmed.
Never substitute an unrelated recent spec for a vetted finding. Derive the output filename in
docs/arc/plans/ using the canonical paths reference.
2. Detect the project and baseline
Detect package manager, framework, test commands, and repository verification commands from
project files (packageManager field, then lockfile, then default npm). If no test runner
exists, use the repository's documented test entry point; if there is no test entry but
other verification scripts exist (typecheck, build, lint), use those. A documented
command that cannot run in the current environment (missing node_modules) is recorded as an
environment prerequisite, never replaced with an invented one.
When no automated verification entry point exists, specify a concrete observable state rather
than inventing a command.
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.
- 2d ago First seen · 191 lines · 34 tokens per session scan A cf424dc9b763
detail is a skill published in the GitHub repository howells/arc (25 stars, last pushed 18d ago), licensed MIT. It adds 34 tokens to every session and 1,807 once invoked, about $0.0002 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 2026-08-30.
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