Write the Memo First

Doesn't matter if you're building a consumer product, B2B software, or sending rockets to Mars. The first thing we write when starting a new business or project is an investment memo. Not a plan. Not a pitch deck. 5 to 8 pages, for an audience of nobody, on what we think the problem is, the target customer, why now, the solution, why you are the one to solve it, and how to get it into the hands of paying customers.

This sounds obvious until you notice that almost nobody starts here. The usual order is the opposite. Open a spreadsheet, scrape an ICP list, run the TAM math, and only after a few weeks of that try to articulate what you actually believe. You end up a month deep in research about a problem you never properly defined.

This matters more now than it used to, because of AI. Used to be that getting good information took real time. Now you can run a deep research report in half an hour. You can have a competitor map by lunch. The constraint has moved. It used to be the research itself. Now it's knowing what to point the research at, and that part still has to come from a human writing down what they believe.

By Friso Paping & Tim de Rooij · 21 April 2026

What this is

We spent this weekend building a Claude Skill that walks a founder through writing an Investment Memo for a new business. The memo is a 5 to 8 page Word document, written in full prose. We tested, iterated, and used the skill on ourselves.

The skill is open source and sits here: github.com/third-vector-eu/claude-skills.

The process

The skill runs five phases. You don't need to memorise them, but knowing what's coming helps.

1. Calibrate. It asks how familiar you are with the domain. Are you a domain expert who has lived in this market for a decade? Adjacent, with related but not identical experience? Or exploring new territory? The answer changes how the rest of the interview runs. Domain experts get harder questions. Explorers get more research support and more humility prompts.
2. Interview. Section by section, the skill walks you through the twelve parts of the memo. Problem, target customer, why now, solution, founder-market fit, business model, go-to-market, competition, customer discovery, risks and falsification, milestones, the ask. For each section it asks three or four sharp questions and runs parallel web research on market signals, competitors, and "why now" evidence. Every answer gets reflected back before moving on.
3. Draft. It writes the full memo in prose. Every major claim gets tagged either [Conviction] or [Hypothesis], so you and any future reader know which parts are earned and which parts are bets.
4. Critical review. This is where the skill earns its keep. It runs the draft against a fourteen-point checklist built around the specific failure modes of early-stage memos. Fluff that looks like content. Contradictions between sections. Weak claims. Missing evidence. Confidence outrunning reality. It then asks you the three sharpest questions, the ones you should sit with this week.
5. Iterate. You answer the critiques. The memo gets revised. A companion document captures the open questions and next experiments that fell out of the review, which becomes the punch list for your next 30 days.

The full process takes between 1.5 and 3 hours, depending on how deeply you think through each answer. Sit with the questions. The slower answers are usually the better ones.

Why write this yourself

You cannot outsource founder conviction. You cannot outsource the felt sense that you are a credible person, or at least a plausible one, to build this company. The act of writing the memo isthe thinking. Someone else writing it for you means you still have to do the thinking later, except now you have a document that sounds like you didn't.

There is a second, quieter reason. The memo is the spine of everything downstream. The pitch deck is an extract of the memo. The website copy is an extract of the memo. The sales messaging, the hiring pitch, the first three blog posts, the cold email to a design partner, the opening talk at your first conference. All of it references the memo. If the memo is weak, every artefact downstream is weak. If the memo is sharp, every artefact downstream inherits the sharpness.

Write it once. Properly. Then the next month's work compounds off it.

It is a living document

The first draft is not the final draft.

You will have ten conversations with prospects and realise your ICP is wrong. You will price something and watch three buyers flinch at the number. You will discover a competitor you had missed. You will learn that the pain point you thought was most acute is actually second, and the real urgency sits elsewhere.

Come back to the skill. Run it again. Revise the memo. What changed between v1 and v2 is where your learning actually lives. Keep the old versions. The delta is the story of your company.

Our tip: read it out loud

When the draft is done, read it out loud. To your co-founder. To your partner. To a patient friend.

Reading it out loud does two things at once. You catch yourself hedging. You hear the sentences where you lose conviction halfway through and start padding. Your voice gets softer. You speed up. You know, as you are reading, which paragraphs do not earn their space.

At the same time, the people listening start asking questions. And the good ones really hurt. The questions you haven't thought about yet. The questions you were hoping no one would ask. Those are the ones you write down, and the answers you go find this week.

Your turn

The skill is on GitHub: github.com/third-vector-eu/claude-skills.

Write yours. Read it out loud. Tell us where it breaks.

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