The AI Second-Order Thinking skill for Claude
You put a plan to Claude and the skill becomes its opponent. Not what is good about it, you have already worked that out yourself, but what happens once the first step is taken, and who benefits if it fails. You get at least three opponents with motive and means, every assumption an evidence label, the consequence chain through to at least the second-order effect, a pre-mortem with five causes of death and concrete choices for this week. Every risk comes with its mechanism attached, because something could happen is not analysis.
the lines above come from the zip on this page · SKILL.md is 16,125 bytes
Plan in, attack out
reg. T.001This is the worked example from the SKILL.md itself, shown here in shortened form. An online shop wants to lower its prices to grab market share. First-order thinking says: lower price, more customers. What happens after that is the question that matters, and who else is sitting at the table when you press that button.
What the AI Second-Order Thinking is
The AI Second-Order Thinking skill is a free skill from our skill library, which by now counts 100 free skills. A skill is an instruction file, SKILL.md, that gives an AI assistant a fixed method for one task: here is how that works exactly NL. No software, no subscription: a single text file of 2,537 words that puts Claude in the role of opponent. The opening line of the file sums it up: you are the opponent of the plan on the table. You are not looking for what is good about it, the user has already done that themselves.
The problem the skill tackles is a structural flaw almost every plan has: the same person comes up with it, judges it and approves it. The file's frontmatter names the complaints literally: everyone is enthusiastic and that makes me nervous, I came up with this plan myself and approved it myself, we have had no pushback on this, I want to know what I am not seeing. A plan without pushback has not been tested, only repeated. This skill organises that pushback, systematically, without needing a colleague brave enough to play the part.
It is written for business owners and teams with a decision that really matters: a launch, a pitch, an investment, a price change, a new market. It is part of the skill library NL that we make available for free from the AI and automation service, with no account and no sales email afterwards.
One thing up front: the attack is an exploration, not a prediction. It does not say what will happen. It says what is plausible once other parties react to your move, and that is something else. And it ends every analysis with a section you rarely get from human advisers: where my attack was weak, with the information needed to test that part too.
Why first-order thinking wrecks plans
First-order thinking stops at the direct effect: lower price, so more customers. Second-order thinking pushes on with the question and then what. In the investing world, the distinction is widely credited to Howard Marks, who worked it out in The Most Important Thing from 2011, and his classic example is in the SKILL.md: first-order thinking says the company is doing well, so buy the stock. Second-order thinking says everyone already knows the company is doing well, so that is already priced in.
The first mistake is the empty chair. The plan states what you are going to do, but not what the others do once you do it. The competitor defending their market share. The existing customer who just paid the old price and wants the difference back. The supplier who does not want their brand positioned as cheap in the market. That is why at least three opponents come to the table, each with motive, means, expected move and the timeframe in which that move happens.
The second mistake is the assumption that passes as fact. Customers choose on price. The competitor reacts slowly. Six months of cash is enough. Every assumption therefore gets a label: strong, weak or untested. The last two always come with the question of what happens if it is wrong, plus the cheapest way to find that out before the market does it for you.
The third mistake is stopping at the first effect. That is exactly where the difference lies between a list of risks and an analysis. In diff form, with the logic from the skill's example:
Six phases, fixed order
reg. T.002Every analysis runs through six fixed phases, and that order is not arbitrary: you cannot think up opponents for a plan that is still vague, and you cannot make choices without the consequence chains. The mono lines below explain why each phase sits where it does.
What is actually in the SKILL.md
A skill is only as good as its instructions, so we simply describe them here. The file opens with a frontmatter that states when Claude should pick the skill up: for explicit requests like red team my plan, attack my plan, what are the second-order effects or play devil's advocate, but also at moments like before I launch, before I pitch and before I invest. And it states when it is not meant to be used: not to write or improve a plan when there is no plan yet, and not for creative or copywriting tasks.
Next comes the method: seven things the skill always does. Ask for the plan as a decision with a date and reformulate it into one sentence. Map at least three opponents. Label every assumption. Write out the consequence chain for at least three major actions through to at least the second-order effect. Run a pre-mortem from a specific moment in the future. Deliver choices for this week, not general recommendations. And finally, name where the attack was weak, meaning which parts of the plan could not be properly tested with the information supplied.
The file contains a mandatory seven-point input checklist, from the decision with budget to the question of what has already been tried and why it did not work. Whatever is missing, it asks for all at once, and then carries on with what is there. The fixed output counts eight blocks: the plan in one sentence, the opponents, the assumptions with evidence, the consequence chains, the pre-mortem, the choices for this week, the signals to monitor, and the section where my attack was weak.
What stands out are the writing rules the skill imposes on itself: clear language addressed directly to you, no hollow superlatives, concrete over abstract, figure over adjective, and the opponent speaking in the first person where that is sharper, because a competitor stating what they are going to do is clearer than an abstract risk. There is also a separate review mode for existing documents, including an [A] marker for every sentence that is an assumption but is presented as a fact. Want to learn to build this kind of instruction file yourself? The full explanation is in writing a SKILL.md NL.
The consequence chain: and then what?
reg. T.003Phase four is where the skill gets its name. For every major action the chain is written out: what happens directly, what happens once the others react to that, and what, in turn, is the consequence of that. The chain below comes from the example in the SKILL.md, including the marker on the most uncertain link.
MOST UNCERTAIN LINK · do they match on everything or only on the bestsellers?
The theory the skill rests on
The SKILL.md names its sources, six titles, and that is deliberate: you can read them yourself and decide whether you agree. The first building block is Howard Marks's second-order thinking from The Most Important Thing from 2011: do not stop at the direct effect, but push on with and then what, and realise that what everyone already knows is no longer an edge.
The second building block is red teaming. The structured form of pushback comes from the programme of the University of Foreign Military and Cultural Studies within the US Army, which is where the Red Team Handbook comes from: techniques for systematically attacking your own assumptions. Business strategist Bryce Hoffman translated that approach into business in Red Teaming from 2017. The third building block is the pre-mortem by psychologist Gary Klein, described in Harvard Business Review in 2007: place yourself at a moment in the future where the plan has already failed and write down why, because that produces sharper answers than the question of what could go wrong.
The file also has three variants that the skill draws on when the context calls for it. The inversion of mathematician Carl Jacobi, made popular by Charlie Munger: do not ask how you succeed but how you guarantee failure, and turn the answers into measures. Devil's advocacy, where one role is tasked with attacking everything, useful in groups. And the analysis of competing hypotheses by Richards Heuer from the intelligence world, for situations where the question is not what could go wrong but what is already going on right now. Anyone who wants that first technique as a standalone skill can find it in the Inversion Thinker skill; the pre-mortem has one too, the Pre-Mortem Analyst skill NL.
Even without installing the skill you can test your plan with these principles: write down three parties who benefit from your failure, label your assumptions honestly, and think through every action at least one order further than you had planned.
What the skill refuses
reg. T.004Under the heading "What the skill never does", the SKILL.md contains seven fixed rules, and that list matters at least as much as what it does do. An opponent that exaggerates or makes things up is not an opponent, just noise. In conversation, those rules play out like this: every rule is a request you might make, with the response the skill gives according to its own instructions.
Installing in Claude Code, Claude.ai or Codex
The zip contains one folder, ai-second-order-thinking, with the SKILL.md inside it. Installing is a matter of putting the file in the right place, and that place differs per environment. SKILL.md has been an open standard since December 2025, so the same skill also works in Codex, Cursor and Gemini CLI. So you are not downloading a Claude file, but a working instruction that any modern AI assistant can read.
- Unzip it into
~/.claude/skills/(or.claude/skills/in your project). - Claude then recognises the skill by itself as soon as you want a plan attacked.
- You can also call it directly, with
/ai-tweede-orde-denker.
- Go to Customize and then Skills.
- Upload the zip there as a skill.
- Or paste the contents of SKILL.md into the project instructions of a Project.
- Open
AGENTS.mdin your repo. - Paste the contents of SKILL.md into it, or place SKILL.md next to it as a separate file and refer to it from
AGENTS.md. - Codex reads that along at every session.
After that, using it is simple: describe your plan with a date and a budget and ask for the attack. The mandatory input checklist makes sure the skill only asks for what is genuinely missing, all at once. If you get stuck anywhere while installing, every step is described in more detail in installing Claude skills NL, and the broader explanation of working with AI is in the knowledge base.
When to use it, and when not to
The file itself is surprisingly precise about this. The full six-phase model is for plans that affect money, reputation or people and cannot be undone within a week. If it is a fast competitive move and there is little time, the skill only runs phase two and four: opponents and consequence chains. If the plan is already fixed and the question is how to make the execution safer, the pre-mortem is enough. And for a small and reversible decision, it delivers a shortened version, with the honest note that a full red-team session would cost more than the mistake itself.
There is a separate mode for existing work. If you hand it a launch document or an investment proposal to review, the skill marks every sentence that is an assumption but is presented as a fact with an [A], checks which parties are entirely missing from the document (usually the company's own customers, its own team, or a platform the business depends on), counts how far the document thinks things through, looks for the missing fallback options, and closes with a pre-mortem and the cheapest tests, ranked on the ratio between cost and information gained.
When do you leave it be? When there is no plan yet: the skill attacks, it does not write. And when your question is actually a different one. If you only want the answer to why a finished plan failed a year from now, the Pre-Mortem Analyst NL is enough. If you are stuck in optimism and want to flip the question, take the Inversion Thinker. And if this is not about this one move but about whether your business can withstand shocks, the Antifragile Thinker is the logical next step: first keep the plan standing, then strengthen the structure underneath it.
Run it yourself, or have it run
reg. T.005This skill is the free do-it-yourself version of thinking work we also deliver as a service. It stays complete and with no catches, but be clear about what a skill is: it teaches your AI how to do something, while every new session starts empty. So a skill is not the engine and not the memory. You prompt, you supply your context again every time, you check. Anyone who wants it differently has two follow-up steps: hand off the engine, or sort out the memory.
where you are now The skill: you are the engine You run the AI Second-Order Thinking skill yourself, in Claude, Codex or Cursor. Costs nothing, works today, and stays entirely in your hands: no trial period, no locked parts. The limit is your own time: the attack only happens when you ask for it, and you have to keep monitoring the signals from phase six yourself afterwards.
only if it recurs The AI employee: usually not the next step here None of our roles fit here, and we would rather say that than sell it to you anyway. The three roles we set up ready-made are the Quote employee (sorting incoming requests and preparing draft quotes), the Sales employee (prospect research and outreach drafts) and the Reporting employee (summaries and weekly and monthly reports from your own data). What this skill delivers, consequence chains and a pre-mortem on your plan, does not fit any of those three. What is possible is a custom role through Mansotti, the company TheSEO trades as, but only if plans worth that kind of scrutiny come through structurally. If this stays a single session a year for you, skip rung 2: being able to read back the consequences you foresaw earlier is worth more, and that is rung 3. What an AI employee does do is on that page.
everything from one source Jarvis: all your AI work from the same company knowledge A skill teaches the AI something; the brain is where that sticks. This skill in particular benefits from that: an attack is only as sharp as its context, and you do not want to retype your competitors, earlier decisions and floor prices every session. Jarvis, the organisation brain, connects ChatGPT, Claude, Codex and your people to the same projects, core knowledge and decisions, so your next AI session does not start over. What that delivers in practice, from the plans to your first week, is at Jarvis itself.
What Jarvis delivers in practice
reg. T.006Rung 3 deserves more than one paragraph, because this is the difference between a clever chat and a system you can build on. Jarvis is the organisation brain: it remembers what your AI tools need to know, divides up the work and keeps track of what happened. You notice it first at the start of a new session.
We have been running on this system ourselves for months. Every agent session, every task and every decision is logged in it and can be read back. A new session therefore does not start blank: it first retrieves the recorded decisions, the running projects and the latest changes, and carries on where the previous one stopped. That is not a promise, that is the workbench we stand at every day.
See the four plans at jarvis/prijzen NL. Through the waiting list NL you only pass on your preferred plan, without obligation. That does not create an account, an order or a payment obligation. We discuss business custom work first.
The skills around it
reg. T.007An attack on your plan rarely stands alone: a decision comes before it and a structural question comes after it. These skills from the same library of 100 each tackle a different piece of that thinking work.
If you have to decide
the decision momentThe attack tests a decision that is already on the table. These three help you make the decision itself.
Cynefin DeciderFirst determines what kind of situation you are in, because a complex problem needs a different approach than a complicated one.SKILL OODA Loop DeciderObserve, orient and decide faster than your environment changes: for when the opponent is already moving.SKILL WRAP DeciderA fixed step-by-step plan against the best-known decision mistakes, for when you have to choose between options.SKILL NLThe same attack techniques on their own
the toolkitThree techniques that sit in this file as a phase or a variant, each also available as a standalone skill.
Pre-Mortem AnalystJust phase five, taken further: the plan has failed, write down why. For plans that are already fixed.SKILL NL Inversion ThinkerThe Jacobi and Munger variant as the main technique: how do you guarantee failure, and flip that around.SKILL Antifragile ThinkerAfter the attack, the structural question: which parts of your business break under a shock and which get stronger from it.SKILLDeeper into the system
the context of the planConsequence chains run through your business and your environment. These three map out that terrain.
Theory of Constraints AnalystFinds the bottleneck that determines where every consequence chain in your system ends up.SKILL PESTEL AnalystThe environmental factors, from politics to technology, that your second-order effects run through.SKILL NL Strategic ThinkingThe broader strategy work that this attack supplies the depth for.SKILL NLLooking further
the contextWhere this skill comes from, and what else there is.
The whole skill libraryAll 100 free skills in one place, sorted by topic.HUB NL AI and automationThe service behind it: from separate skills to working automation in your business.SRV AI trainingIf your team wants to learn to set this kind of work up itself.SRV NL Knowledge baseSearchable articles about SEO, AI and online visibility.DOCFrequently asked questions
What does the AI Second-Order Thinking skill cost?
Nothing. The skill is free, falls under the MIT licence, and you do not have to create an account or leave an email address. You download a 6.6 KB zip containing a folder and a single file, SKILL.md, and that is the complete skill. There is no paid version and no sales email follows.
Does this skill also work in Codex, Cursor or Gemini CLI?
Yes. SKILL.md has been an open standard since December 2025, so the same file also works in Codex, Cursor, Gemini CLI and other tools that follow the standard. In Codex you unzip it into .agents/skills/ in your project, or into ~/.agents/skills/ for all your projects; Codex has supported SKILL.md directly since the open standard of December 2025. Putting the contents of SKILL.md into your AGENTS.md still works too. The instructions themselves are just plain readable text, so any AI assistant that accepts instruction files can work with them.
What is the difference between second-order thinking and a pre-mortem?
A pre-mortem is one of the six phases of this skill: you place yourself at a moment where the plan has already failed and write down the causes of death. Second-order thinking is broader. It also maps the opponents, tests your assumptions for evidence, and writes out the consequence chain per action through to at least the second-order effect. If you only want that one technique, there is a separate pre-mortem skill in the same library.
Does the skill invent competitors or figures?
No. Inventing figures, market shares, client names and research results is on the list of things the skill never does. It does not introduce real company names you have not supplied: it uses the role instead, such as biggest competitor or new entrant. Every risk it names must also have a mechanism, meaning how it happens, not just that it could happen.
Can I also have an existing plan or document reviewed?
Yes, the skill has a separate review mode for that. You then get an assumption marker where every sentence that is an assumption but is presented as a fact gets an [A], a check for which parties are missing from the document, a count of how far the document thinks things through, the missing fallback options, five causes of death via a pre-mortem, and a list of the cheapest tests, ranked on the ratio between cost and information gained.
Is not the full model too heavy for small decisions?
The skill thinks so too. The full six-phase model is meant for plans that affect money, reputation or people and cannot be undone within a week. For a small and reversible decision it delivers a shortened version and notes that a full red-team session would cost more than the mistake itself. For a fast competitive move it uses only the opponents and the consequence chains.
What does the skill need from me to be able to work?
The plan or decision with a date and a budget, the direct result you expect, who your competitors are, which parties are affected, what becomes irreversible once you start, what has already been tried and how firmly the plan is already fixed. That checklist is in the file itself. If anything is missing, the skill only asks for that, all at once, and then carries on with what is there.
First, know where you stand now
The sharpest second-order question for most businesses, incidentally, is not about a new plan, but about the status quo: what happens if your customers can no longer find you tomorrow, and who benefits from that? The free SEO scan shows in a few seconds where your site stands, before a competitor answers that question for you. In the guide eight decision models compared NL you can see how this model relates to the others. And if you want to talk further about what AI can do for your business, from separate skills to full automation, we are happy to simply talk about that.