Thursday Skill

The Munger test

Charlie Munger's inversion as a skill, so before a big decision Claude lists the surest ways it could fail instead of agreeing with you.

Step One, Set It Up

In Claude Code, open a chat in the folder that holds your business and paste this in. Claude writes the skill, six steps in order, and shows you the file before you use it. Because it lives in that folder, it reads what you already keep there about your offers, prices and clients before it says anything.

Paste this into Claude Code

Write me a skill called munger-test, for a big decision I'm about to make. Write its description as the sentences I actually say, like "Munger test this" and "how would this fail", and say it is for a price rise, a hire, a new supplier, a programme I'm being sold or a big client, never a small choice. When it runs, it does this, in order: 1. Says my decision back to me in one sentence, and what I want to get from it, and asks me one question if either is unclear. 2. Reads what this folder already holds about my business before it writes anything, and tells me which files it read. 3. Turns the question round, the way Charlie Munger did, and lists the surest ways to make this decision fail, specific to my business, the likeliest first, never ones that would sink any business. 4. Checks my plan against each one and tells me whether my plan already does it, might do it, or avoids it, with the line from my files that shows it. 5. Turns each way to fail into a rule for what not to do, and for each one my plan breaks, the cheapest way to fix it or check it before I commit. 6. Ends on the two my plan is closest to, and leaves the decision to me. It writes nothing else and sends nothing. Show me the file.

Step Two, Before Any Big Decision

Before a price rise, a hire, a new supplier or a programme you are being sold, say Munger test this. It asks what you want from the decision, lists the surest ways to make it fail, checks your plan against each one, and tells you which ones you are already doing, each with a rule for what not to do and the cheapest way to fix it before you commit. Then the decision is yours.

Every time

Munger test this. Ask me what the decision is first.

In The Claude App Instead

With no folder for a skill to live in, paste this into a new chat each time. It asks you about your business rather than reading it, so give it the detail it asks for.

Run it once

I'm about to make a big decision. Test it the way Charlie Munger would, by turning it round. Ask me what the decision is and what I want from it, one question at a time. Then list the surest ways to make it fail for a business like mine, likeliest first, check my plan against each, and turn each into a rule for what not to do. End on the two my plan is closest to, and never tell me whether to go ahead.

Why It Works

Ask Claude whether something is a good idea and it builds you the case for it, and if you sound keen, it tells you probably yes. Charlie Munger, Warren Buffett's business partner for decades, turned the question round. He borrowed a line from the mathematician Jacobi, invert, always invert, and worked out how to get what he wanted by studying how to get the opposite, like the countryman who said he wished he knew where he was going to die, so that he would never go there. Asked how a decision would fail, Claude has nothing to agree with.

Munger set the method out in his 1986 commencement speech at the Harvard School, How to guarantee a life of misery, which answers how to have a good life with a list of sure ways to a miserable one.

One Honest Bit

It finds the ways a plan can go wrong, and it cannot tell you the decision is right, which is the point. It is only as sharp as what it knows about your business, so the skill in a folder that holds your offers and clients finds far more than the one message in the app, and anything it says your files do not cover is worth checking with the person who would know.

Want to get better at this?

Let's set up your agent ecosystem.

This page is one job. The whole thing is a set of them running off the same foundation, the folder your AI works out of, the brief on how you like things done, the accounts it can reach and the skills that run off all of it, so your admin gets done the way you would do it. It is what I teach one to one, on your own machine and against your own work, and the quickest way to find out what yours would look like is a proper chat about it.

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