(2025-12-16) Klein How To Build Your Pm Second Brain With Chatgpt

How to build your PM second brain with ChatGPT. Lenny Rachitsky: Someone smarter than me once said, “AI won’t replace you, but a person using AI better than you might.” Amir Klein is already that person and has written a guide for the rest of us.

The first month in my new role at monday.com, I was tasked with building our first AI agent. The goal was to create an AI co-pilot, something users could turn to for insights, explanations, or building complex workflows they wouldn’t know how to create on their own.

To build that, I needed a ton of context—all the internal knowledge, decisions, assumptions, and scattered inputs that shape any product direction. And gathering all of that felt completely overwhelming.

I was drowning.

All that context lives everywhere

I dumped everything I had into a ChatGPT Project, word-vomited all that was on my mind, and asked if it could help me get started. And boy, did it.

Finally, I felt like I could smell a roadmap on the horizon, a direction was forming, and things began to click. Even better, I felt somewhat in control without being stressed about storing everything in my head. I could store it in the AI instead—a second brain.

My good friend Tal Raviv taught us how to think with AI. I’m building on Tal’s post by showing what happens when AI becomes an extension of your mind—when it carries your context, grows alongside you, and ultimately amplifies what you’re capable of as a PM.

No matter what we’re doing, we’re constantly trying to hold way too much information in our heads. But the hardest part isn’t just carrying it; it’s that none of these pieces arrive neatly fitted together. Context comes in fragments: user feedback, metrics, market changes, internal constraints, past decisions, intuition.

As PMs, our job is to assemble those pieces into a clear picture—shaping the problem, forming the hypothesis, and defining the solution space

Doing that synthesis in your head, and doing it over and over again, can literally feel impossible.

That’s where AI comes in. When you feed in all of that context that you’ve been trying to juggle yourself, your ChatGPT Project becomes a second brain that can store the information and synthesize it for you.

It’s important to say: using a second brain doesn’t dull your role but actually sharpens it. Your reasoning, product sense, knowledge, and taste are still doing the real work; AI just amplifies them. You can’t outsource judgment or creativity

Step 1: Create its personality

Once you’re inside, if you approach Projects like a second brain that you’re growing, you want to first make sure it thinks in the way you think. In other words, you need to build its personality. Each Project has an instructions section where you can first define this “personality” in plain language.

A really awesome way of doing this is with the help of ChatGPT (of course). Open a new chat and describe what you want

Step 2: Feed it information

Go to “Add files” and just dump it in.

I think the biggest “whoa” moment for me is realizing that everything is essentially text. The classics, like PRDs and docs, are a given, but decks, websites, Excel/CSV sheets, dashboards, and pp channels all contain text too. They just need to be exported into pps and then you can upload them into the files section too.

I’ll scroll through a massive Slack channel that’s gotten impossible to navigate. I’ll export it or, if that’s not possible, I’ll copy and paste the entire channel’s contents into a doc and save it as a PDF. Then I drop it into the Project

When I need it to understand our product’s capabilities, instead of rambling on to it about how my product works, I go to our support or docs site, hit Command + P, and save the entire page as a PDF to drop in

In the case of the first initiative I led at monday.com, I started with a few decks that different colleagues of mine had made, downloaded PDFs of monday.com documentation pages explaining how specific things work, and added a bunch of CSV files containing Reddit threads of conversations thousands of people had about monday.com in relation to AI and our competitors.

The beauty of Projects is that you’ll start creating new artifacts from it. Whatever it is you’re creating—whether it be PRDs, overview docs, or strategy decks—once finished, you can take those, put them in a doc, download them, and feed them back into your second brain

you can lean on it for everything that you don’t want to do but needs to get done

1. Sign-up forms

2. Prototypes

Sometimes, when I’m deep in a conversation with the Project, we’ll hit a moment where the idea feels stuck in theory. We’re talking about flows, interactions, edge cases, but it’s all abstract. So I’ll say:
“Let’s make this real. Write me a prompt for Lovable that builds this experience.”

It’s not just a “wow” moment—it’s a workflow. A prototype like this lets me gather my designer and engineer, show them the idea, and get feedback before anyone has to build.

3. Tailored communications

When you zoom out, PM work is full of moments where you need to communicate the same initiative from a completely different angle. It happens daily.
None of these tasks are hard because of the writing itself. They’re hard because you have to mentally reload the context, remember what matters to each audience, and then translate the same initiative in so many different ways. That reload cost is enormous! My second brain removes that step entirely

Context is the new interface

As PMs, context is the raw material we think with. It’s how we spot patterns others miss. It’s how we distinguish noise from signal. It’s how we turn a vague cluster of symptoms into a crisp problem statement that we rally around. When all that context lives only in your head, your output is limited by your working memory

You don’t just remember more. You reason better.

At monday.com, we saw the same pattern for months with our customers: they loved the idea of AI in our product, but they had no idea how to start

Within minutes of my blabbering everything on my mind to Projects, it surfaced the key pain point for our users: they weren’t blocked by capability but by confidence. They needed scaffolding, not features. That insight alone unlocked the product direction we eventually shipped—and it was a huge success!

Appendix: Using Claude or Gemini as your second brain...