Build An AI Second Brain

Your notes app stores what you write and then waits for you to come back and read it. A second brain built on Claude and Obsidian reads everything you feed it, pulls out the key concepts, links them together, and lets you search your entire knowledge base from one place. It never forgets, and it gets smarter the more you use it.

What You'll Learn

• What an AI second brain actually is and why it beats a plain notes app
• How to install Obsidian and the free Claude skill that builds the brain for you
• The exact commands to feed it data, research topics, and query it with citations
• What to feed it first and the powerful systems you can build on top of it

What You're Building

You're building an AI second brain that never forgets, understands the connections between all your notes, research, and projects, and gets smarter the more you use it. It reads everything you feed it, pulls out the key concepts, links them all together, and lets you search your entire knowledge from one place.

What You Need

• Claude Code installed
• About 10 minutes for setup
• Your notes, files, and research (anything you want the brain to know)
• No coding or technical experience required

Step 1: Install Obsidian

Download and install Obsidian. This is where your AI brain will live. It's free and runs on Mac, Windows, and Linux.

Download from: https://obsidian.md

Obsidian is a note-taking app that stores everything as plain text files on your computer. It has a graph view that lets you see how all your notes connect visually, which is the magic of the second brain.

Step 2: Install The Skill From GitHub

This is the skill that tells Claude exactly how to read your notes and data, pull out the key concepts, and link them all together into a self-organizing second brain.

git clone https://github.com/AgriciDaniel/claude-obsidian
cd claude-obsidian
bash bin/setup-vault.sh

Then open the folder in Obsidian: Manage Vaults > Open folder as vault > select the claude-obsidian folder.

Step 3: Run The Skill And Feed It Your Data

Open Claude Code in the same folder. Type /wiki. Claude sets everything up. Then give it access to your notes and files and watch your second brain grow.

To view it, open Obsidian, click graph view, and you can see everything fully mapped: every note, file, and project connected.

The core commands:

/wiki                 Set up and scaffold your brain
ingest [file]         Feed it a source, Claude builds wiki pages
/autoresearch topic   Claude researches a topic and builds pages
/save                 Save conversation insights to your brain
/query question       Ask your brain a question with citations

What To Feed It First

The more you feed it, the smarter it gets. Start with:

• Meeting transcripts and notes
• Articles and blog posts you've saved
• Podcast transcripts (pull with SupaData)
• Book highlights and summaries
• Research papers and reports
• Project documentation and specs
• Brain dumps and random thoughts

What You Can Build With Your Second Brain

Once your brain has content, you can use it to build some seriously powerful things:

• Client databases that remember every detail and conversation you've ever had with them
• Full memory of your Claude sessions and tasks so you save tokens and never lose context on projects
• An AI chief of staff that knows your projects, tasks, calendar, and notes and gives you a daily briefing every morning
• Competitor intelligence reports that pull from everything you've collected across months
• Content research that compounds: every video, podcast, and article you consume makes your scripts sharper

Why It Gets Smarter Every Session

Normal Claude starts fresh every session. This brain maintains a hot cache that persists between sessions. Every time you reopen Claude, it starts with full context of what you were working on, what you've covered, and what's new. Every answer gets saved back so the brain compounds. Build it once. It gets smarter forever.

Go Deeper

• Printable PDF version of this guide: https://drive.google.com/file/d/1sq1ssyWlfKoAxURCrjJoR21Cvkd8DKmH/view?usp=drivesdk

Want the whole system installed live, with Cooper on the call? Build Your Own AI, the two week sprint runs the first two weeks of August.

Or get a new working tool every Monday inside The AI Operator community on Whop.