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 simbajigege/book2skills --skill common-sense-index-investing-boglegit clone --depth 1 https://github.com/simbajigege/book2skillsWrote 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/simbajigege/book2skills/common-sense-index-investing-bogle)<a href="https://agentmods.dev/skills/simbajigege/book2skills/common-sense-index-investing-bogle"><img src="https://agentmods.dev/badge/skills/simbajigege/book2skills/common-sense-index-investing-bogle/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/simbajigege/book2skills/common-sense-index-investing-bogle"><img src="https://agentmods.dev/badge/skills/simbajigege/book2skills/common-sense-index-investing-bogle.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00038 | $0.02069 |
| Opus 5 | $0.00019 | $0.01035 |
| Sonnet 5 | $0.00008 | $0.00414 |
| Haiku 4.5 | $0.00004 | $0.00207 |
Grade A, and why
common-sense-index-investing-bogle 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 12d 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 — 206 lines — stays where its author put it; the contents beside it link to each section on GitHub.
The Little Book of Common Sense Investing — Index Investing Skill
Knowledge source: The Little Book of Common Sense Investing by John C. Bogle.
Overview
Use this skill to evaluate investment fund choices, portfolio simplicity, cost drag, index fund discipline, asset allocation, and buy-hold behavior using Bogle's common-sense investing framework. It is educational decision support, not personalized financial advice.
When to Use This Skill
Use this skill when the user asks:
- "Should I use an index fund or active fund?"
- "Are these fund fees too high?"
- "How should I think about ETFs, smart beta, or advisers?"
- "What stock/bond allocation is sensible?"
- "Am I overcomplicating my portfolio?"
Core Principle
Own the broad market at very low cost and hold it for the long term. Before costs, investors collectively earn the market return; after costs, the more they pay intermediaries, trade, and chase winners, the less they keep.
Workflow Inventory
| Workflow | User question pattern | Inputs | Steps | Output | Independent trigger? | Distinct references? | Triage score | Should be subskill? | Reason |
|---|---|---|---|---|---|---|---|---|---|
| Fund comparison | "Which fund should I choose?" | Fees, turnover, strategy, benchmark, tax status | Compare cost, diversification, active risk, simplicity | Fund verdict | Yes | Yes | 3 | No | Primary index-investing workflow. |
| Cost drag analysis | "Do fees matter?" | Expense ratio, turnover, horizon | Estimate compounding drag | Cost warning | Yes | Yes | 3 | No | Same decision report. |
| Asset allocation | "How much stocks/bonds?" | Age, horizon, risk capacity, income need | Apply simple stock/bond discipline | Allocation range | Yes | Yes | 3 | No | Fits the same portfolio policy. |
| Product skepticism | "Should I buy ETF/smart beta/adviser pick?" | Product structure, costs, incentives | Check complexity, trading temptation, conflicts | Use/avoid verdict | Yes | Yes | 3 | No | Same Bogle cost/simplicity lens. |
What ships with it
5 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.
- 12d ago First seen · 206 lines · 38 tokens per session scan A 6058c37e29bb
common-sense-index-investing-bogle is a skill published in the GitHub repository simbajigege/book2skills (163 stars, last pushed 17d ago), licensed MIT. It adds 38 tokens to every session and 2,069 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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