Buffett-style moat and margin-of-safety check
OfficialOfficial · updated Nov 4, 2026 · v1.0.1
Checks a business or a purchase for an enduring moat, a known circle of competence and a margin of safety, as Warren Buffett describes them in the Berkshire letters. Not investment advice.
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When to use it
- You want to know what really protects your business from competitors
- Before buying a company or making a large long-term commitment
What you give it
- What the business sells and earns
- Competitors and switching options
- Evidence: margins, retention, cost per unit
- Price and value estimate, with assumptions
What you get
A three-part verdict with a moat table, a circle-of-competence table, a margin of safety recomputed under worse assumptions, and what to find out first.
Changelog
- v1.0.1 · Nov 4, 2026 · Example output now opens with the attribution and not-affiliated lines, as the skill's own checks require.
- v1.0.0 · Nov 4, 2026 · First release.
Sources
- Berkshire Hathaway 2007 shareholder letter (an enduring moat) (2026-11-04)
- Berkshire Hathaway 1996 shareholder letter (circle of competence, economies of scale) (2026-11-04)
- Berkshire Hathaway 1992 shareholder letter (businesses we understand, margin of safety) (2026-11-04)
- Berkshire Hathaway 1993 shareholder letter (brand, product, distribution as a moat) (2026-11-04)
- Berkshire Hathaway 1995 shareholder letter (low operating costs, GEICO's moat) (2026-11-04)
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- Munger-style inversion review Reviews a plan by inversion: lists how it would surely fail, separates what the business couldn't survive, and checks it through several models, from ideas Charlie Munger described.