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/stchiotis/library-first-engineering/lfe-perf-checknpx skills add StChiotis/Library-First-Engineering --skill lfe-perf-checkgit clone --depth 1 https://github.com/StChiotis/Library-First-EngineeringWrote 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/stchiotis/library-first-engineering/lfe-perf-check)<a href="https://agentmods.dev/skills/stchiotis/library-first-engineering/lfe-perf-check"><img src="https://agentmods.dev/badge/skills/stchiotis/library-first-engineering/lfe-perf-check.svg" alt="Measured on agentmods" 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 | $0.00072 | $0.01058 |
| Opus 5 | $0.00036 | $0.00529 |
| Sonnet 5 | $0.00014 | $0.00212 |
| Haiku 4.5 | $0.00007 | $0.00106 |
Grade A, and why
lfe-perf-check 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 6d 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 — 94 lines — stays where its author put it; the contents beside it link to each section on GitHub.
LFE Performance Check — Prompt-Based Anti-Pattern Analysis
Position in Pipeline
- Phase: 3 (Inspector sub-skill)
- Persona: Inspector (read-only; no src/ writes)
- Trigger: Invoked by
/lfe-inspectorSub-Skill Dispatch whenlfe-perf-check: truein.docs/quality/inspector-config.md - Output:
.plans/checks/perf_findings.md— aggregated by Inspector intocritique.md
Mission
Detect performance anti-patterns introduced by the current implementation through structured LLM reasoning over the diff. Findings are advisory unless a pattern is provably unbounded (e.g. O(n²) in a hot path with no upper bound on n).
Hard Rules
- Dispatch Context Required (refuse direct invocation): This skill is dispatched by
/lfe-inspectorStep 6 — it is not a Brain-typeable skill (perLLM_AGENT_GUIDE.md§8.8 Skill Invocation Authority). If invoked without.plans/builder_done.mdfor the current slice, halt immediately and reply: "/lfe-perf-checkis an Inspector sub-skill dispatched by/lfe-inspector. It cannot be run standalone. Run/lfe-inspector— the dispatcher will invoke this sub-skill if it is enabled in.docs/quality/inspector-config.md(or via an## Inspector Overridessection inactive_plan.md)." Direct invocation produces orphaned findings files and breaks the Inspector's aggregation logic. - Prompt-Only: No profiling tools, no benchmarks, no execution. Reasoning over code only.
- Diff-Scoped: Analyse only files listed in
builder_done.md; skip unchanged code. - Severity: Critical (provably unbounded, certain production impact) / High (likely hot-path) / Medium (probable overhead) / Low (style concern).
- Cite Line: Every finding quotes the specific pattern from the code.
Inputs
.plans/builder_done.md— list of changed files.plans/active_plan.md— domain context and scope boundary.docs/domain/— domain rules that might imply expected data volumes
Workflow
Step 1: Extract Diff Scope
From builder_done.md, identify and read modified files.
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.
- 6d ago First seen · 94 lines · 72 tokens per session scan A 5e18659f1734
lfe-perf-check is a skill published in the GitHub repository StChiotis/Library-First-Engineering (43 stars, last pushed 1mo ago), licensed MIT. It adds 72 tokens to every session and 1,058 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 2026-08-30.
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