AI Berkshire is a collection of Claude Code and Codex skills that structures investment research around the methods of four value-investing thinkers and uses multiple agents for adversarial analysis. It is intended for investors who want a disciplined process for researching companies and making valuation-based decisions.
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 xbtlin/ai-berkshire --skill investment-memo-craftgit clone --depth 1 https://github.com/xbtlin/ai-berkshireWrote 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/xbtlin/ai-berkshire/investment-memo-craft)<a href="https://agentmods.dev/skills/xbtlin/ai-berkshire/investment-memo-craft"><img src="https://agentmods.dev/badge/skills/xbtlin/ai-berkshire/investment-memo-craft/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/xbtlin/ai-berkshire/investment-memo-craft"><img src="https://agentmods.dev/badge/skills/xbtlin/ai-berkshire/investment-memo-craft.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 | $0.00093 | $0.02055 |
| Opus 5 | $0.00046 | $0.01027 |
| Sonnet 5 | $0.00019 | $0.00411 |
| Haiku 4.5 | $0.00009 | $0.00205 |
Grade A, and why
investment-memo-craft 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 13d 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 — 153 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Investment Memo Craft
Purpose
Turn investment research into a decision-ready Codex research report. Keep the data discipline of the underlying research skill, but make the output easier for an investor to use: concrete business mechanics, sharp inverse thinking, explicit opportunity cost, action thresholds, and calm Markdown typography.
Use this as a writing and judgment overlay. It does not replace financial-data rules, primary-source checks, valuation tools, or report audit tooling.
For long-form AI Berkshire outputs, title the artifact as a "research report" by default. Use "investment memo" only when the user explicitly asks for a memo format.
This is a Codex-only hand-written skill kept under codex-skills/ for simple installation. Do not add a same-named skills/investment-memo-craft.md source unless intentionally adopting this workflow for Claude Code too.
Core Workflow
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Open with context; reserve the full decision for after the evidence.
- In the first screen, state the research date, price, market cap, valuation, and a short thesis.
- Do not front-load the full buy/hold/sell table unless the user explicitly asks for an executive memo.
- Put the detailed recommendation, investor-specific actions, and price bands near the end, after business quality, risk, and valuation have been argued.
- Separate "good business" from "good investment at this price".
-
Build the operating map before the philosophy.
- Include revenue structure, segment economics, unit drivers, and 3-5 year trends early.
- For asset-heavy businesses, show the key assets individually when they explain the moat.
- Explain the pricing mechanism, customer lock-in, cost structure, and reinvestment needs.
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Compress business essence into one memorable sentence.
- Prefer a sentence that describes who pays, why they pay, what is scarce, and what repeats.
- Avoid generic labels such as "industry leader" unless followed by the mechanism that makes leadership durable.
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.
- 13d ago First seen · 153 lines · 93 tokens per session scan A 2d6217f3589f
investment-memo-craft is a skill published in the GitHub repository xbtlin/ai-berkshire (16,289 stars, last pushed yesterday), licensed MIT. It adds 93 tokens to every session and 2,055 once invoked, about $0.0005 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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