How to build a second brain your AI can actually use

You have probably got notes everywhere. A few in your phone, some in a notes app you opened once, a pile of screenshots, half-finished thoughts buried in old chats. And when you actually need one of them, you cannot find it. So you give up and just try to remember.

I am Alex. I co-founded AgentPod, where we test and security-check AI skills for a living, and the single most common wish I hear is some version of this: I want my AI to just know my stuff. Not the whole internet. My stuff. My notes, my ideas, the things I keep having to repeat. That is what a second brain is for, and the good news is you can build one without being technical.

Let me show you what it actually is, why a folder of docs is not it, and how I would set one up step by step.

A folder of docs is not a second brain

Most of us already have a folder somewhere full of documents we meant to read again. Meeting notes, saved articles, that one PDF. It feels organized. But be honest: when did you last reopen anything in it?

That is the difference. A folder of docs is a place things go to be forgotten. A second brain is a place your AI can search and pull from on demand. The notes are the same. What changes is that something can now read them for you and answer questions using them.

Picture it like a brilliant assistant who has read every note you ever wrote and never forgets where you put anything. You ask, they answer, citing the note. That is the feeling we are building toward.

Why this matters more than it sounds

Out of the box, your AI forgets. Close the chat and most of what you told it is gone. So you re-explain your project, your preferences, your context, over and over. It is exhausting, and it is the number one complaint I hear.

That is nearly three out of four people tired of repeating themselves to a tool that is supposed to help. A second brain fixes the root cause. Instead of the AI relying on its own shaky short-term memory, it reads from a store you control. I wrote a whole piece on this if you want the why behind it: why your AI forgets.

And if the word skill is still fuzzy for you, it is just a saved set of instructions that teaches your AI to do one job well. Here is the plain version: what is an AI skill.

What goes into a second brain

You do not need a perfect system. You need one place and the habit of putting things in it. Here is the kind of stuff that belongs:

• Notes and ideas: the half-thoughts you would otherwise lose. Jot them down rough. The AI tidies them later.
• Reference material: meeting notes, articles you want to remember, how-tos, decisions you made and why.
• Context about you: how you like things done, your projects, your people, the facts you keep having to re-explain.
• Things you will need again: account details (the non-secret kind), recurring instructions, templates you reuse.

How to set one up, step by step

This is the part people overthink. It is genuinely four moves. I will use a notes app you may already have, like Notion or Obsidian, because that is where most people already live.

1. Pick one home for everythingChoose a single place: Notion, Obsidian, Apple Notes, whatever you will actually open. The app matters less than the rule. One place. Stop scattering notes across five tools.
2. Start dumping notes inFor a week, every time you have a thought, a meeting, a saved link, put it there. Do not organize it. Just capture. You are feeding the brain. Twenty or thirty notes is already enough to feel the difference.
3. Connect it to your AIThis is where a skill does the heavy lifting. A second brain skill links your notes to ChatGPT or Claude so it can read and search them. You are not writing code. You are pointing the AI at your shelf and saying: this is mine, learn from it.
4. Start asking it questionsNow use it. What did we decide about pricing last month? Summarize my notes on that project. What do I keep forgetting to do? The AI pulls the answer from your notes, not from thin air. That is the whole payoff.

The two skills I would reach for here do exactly these jobs. The first turns your notes into something the AI can query. The second keeps it synced with the app you already use, so you never have to copy and paste.

Second BrainTurns your notes into a memory your AI can search and recall on demand.View skill →

Notion / Obsidian SyncKeeps your second brain synced with Notion or Obsidian, no copy and paste.View skill →

Memory for the moment, memory for the long haul

There are really two kinds of memory worth knowing about, and they work together.

One is your second brain: the notes and reference material you deliberately put in. The other is persistent memory: the AI quietly remembering facts about you across conversations, so it stops asking the same questions. You tell it once that you prefer short replies, or that your co-founder is named Sam, and it sticks.

Persistent MemoryYour AI remembers your preferences and facts across every chat, so you stop repeating yourself.View skill →

Together they cover both ends: the big searchable library of your notes, and the small running memory of who you are and how you like things. That is when an AI stops feeling like a stranger every morning.

Here is an example of the kind of prompt that only works once you have a second brain in place. Try it after you have captured a few weeks of notes.

Look through my notes and answer:

1. What were the three biggest decisions I made this month, and why?
2. Is there anything I wrote down that I said I would follow up on but never did?
3. Summarize what I currently think about [your project] in five bullet points.

Use only my notes. If you are not sure, say so.

That last line matters. A good second brain answers from your notes, not from guesswork, and it tells you when it does not know. That honesty is what makes it trustworthy.

The easiest way to start

If picking individual skills feels like one decision too many, we bundled the memory pieces together so you get the whole setup in one go: the second brain itself, the sync, and the recall, ready to use.

Two out of three people tell us they would rather have a small vetted shelf than wade through thousands of options, and I am firmly in that camp. Start with the bundle, add notes, and let it grow with you.

Common questions