Second brain · 20 min

Build a company second brain in Copilot

Copilot app, Notebooks, SharePoint, Copilot Cowork

Jump to the prompts ↓

Short answer: Open the Copilot app, select Notebooks, then All notebooks and New notebook. Add a short Start here rules file and an index first, then your sources, and paste your rules into the notebook instructions. Keep wiki pages as markdown (.md) files. Copilot Chat users can upload up to 50 files. With Microsoft 365 Copilot you can add SharePoint folders, and Copilot uses only the 300 files most relevant to each prompt.

Last checked against Microsoft docs: Oct 21, 2026

You've seen people build a second brain with Claude and Obsidian. This guide is adapted from Andrej Karpathy's method and early Microsoft adopters. It's one way to set it up in Copilot, not a standard everyone follows.

What a second brain is

Andrej Karpathy described an "LLM wiki" in an X post and an idea file on GitHub. You keep raw sources, and AI compiles them into linked markdown pages. Copilot has a place for each part.

Use markdown, not Word. Copilot Notebooks now work with markdown (.md) files, and Karpathy's method, early adopters and Microsoft's own team knowledge base all use markdown pages. Plain text is easy for Copilot to read and write.

Before you start: run the oversharing check so Copilot only finds files people should see.

Pick your tier

Beginner: memory plus one notebook

Needs: Microsoft 365 Copilot Chat, with a SharePoint or OneDrive license to create notebooks. Not sure what you have? Start here.

1. Set custom instructions: in Copilot, open Settings and more, then Chat settings, then Personalization, then Edit instructions. Add your role and writing style. Memory works with and without a Microsoft 365 Copilot license, and this part is personal to you. Copilot memory is in preview, and an admin can turn it off.
2. Open the Copilot app, select Notebooks, then All notebooks, then New notebook.
3. Upload 00 Start here.md and 00 Index.md first, then your source files.
4. Paste the "How to answer" lines from Start here into the notebook instructions.

Copilot Chat users can add up to 50 references, and all 50 are used. Uploaded files are copies, so upload the new version when a file changes.

Intermediate: a SharePoint library with a notebook or agent on top

Needs: Microsoft 365 Copilot, with edit access to a SharePoint site. Not sure what you have? Start here.

Company Brain (SharePoint site)
  00 Start here.md   (short rules, points to each CONTEXT.md)
  00 Index.md
  00 Change log.md
  01 Sources/        (owners edit, everyone else reads)
     Policies/  Product/  Meetings/  (approved notes)
  02 Wiki/
     Pricing/   CONTEXT.md  + topic pages (.md)
     Onboarding/ CONTEXT.md + topic pages (.md)
  03 Answers/        (good answers filed back in)

1. Create the site and folders. Make 01 Sources read-only for most people.
2. Write 00 Start here and 00 Index using the template below and save them to the site root. Give each wiki topic folder a short CONTEXT.md that says what the topic covers and which sources it uses.
3. Create a notebook and add 00 Start here and 00 Index directly, then add the 01 Sources and 02 Wiki folders.
4. Paste the "How to answer" lines into the notebook instructions.
5. When the team relies on it, build a SharePoint agent on 01 Sources and 02 Wiki so people can ask without opening the notebook.

Cloud references stay current, so answers follow the latest version of each file. When you add a folder or site, Copilot uses only the 300 files most relevant to each prompt. Add key files directly so they are always used.

Advanced: Copilot Cowork or a SharePoint team knowledge base

Needs: For Copilot Cowork, a Microsoft 365 Copilot license plus Copilot Credits billing, which an admin turns on. Your admin may also need to join the Frontier program before the setting shows up. The team knowledge base preview needs the Frontier program. Not sure what you have? Start here.

In a notebook, Copilot drafts pages and a person saves them. In these two options, Copilot can write the pages itself, which is closer to Karpathy's method.

Developer builds go further, such as Copilot Studio agents with knowledge sources. Each agent can point at up to twenty-five SharePoint sites with generative orchestration. If your notes are in OneNote, note that Agent Builder can use OneNote pages but, per a Power Platform Community thread, full Copilot Studio can't. Save the pages as PDF instead.

Expert calls and builds are a paid service. They never affect what we recommend in the guides.

Automate intake

Getting new sources in is the slow part. Early adopters have used these:

• Power Automate export: a nightly flow that exports a task board or case list to an Excel file the notebook references.
• Scheduled Cowork skills: skills that pull email on a schedule, convert it to markdown and drop it into the intake folder.
• Scheduled prompts: a Copilot scheduled prompt that writes a daily summary.

Garbage in means garbage out. Pick each feed on purpose, and keep a person checking what lands in the wiki.

The Start here template

Keep it short and send Copilot to the topic files for detail. Anthropic's advice for CLAUDE.md is under 200 lines. Microsoft gives no size limit for this file, so use the same target.

START HERE (read this first)
Company: [name], [what we sell, one line], [who buys it]
Topics: for detail, read the CONTEXT.md in each folder
  - 02 Wiki/Pricing/CONTEXT.md
  - 02 Wiki/Onboarding/CONTEXT.md
Words we use: [term = meaning], [product names, correct spelling]
Sources of truth: policies live in 01 Sources/Policies. If a wiki page
  disagrees with a source, the source wins.
How to answer:
  - Answer only from this notebook's references.
  - Name the file for every fact.
  - If it is not in the references, say "Not in our files" and name who to ask.
  - Mark anything older than [12] months as POSSIBLY OUT OF DATE.
Do not: give legal or HR advice, guess prices, include customer personal data.
Owner of this brain: [role]. Last reviewed: [date].

Copy these prompts

Prompt 1: set it up

Read 00 Start here and the most relevant references in this notebook. Then:
1. Draft 00 Index: one line per topic, the file that covers it, and the owner.
2. List topics that have sources but no wiki page yet.
3. Write the wiki page for [first topic] in markdown with these sections:
   What it is, How we do it, Who owns it, Open questions, Sources.
Cite a file after every fact. If two files disagree, list both under
Open questions and do not pick one.

(Prompt from stuckwithcopilot.com/guides/copilot-notebook-project/)

Prompt 2: weekly update

These sources were added or changed this week: [file names].
Using only those files and 00 Start here:
1. Summarize each in 5 bullets, citing the file.
2. List which pages in 02 Wiki each one changes, and what to change.
3. List new terms for the Words we use list.
4. Write one change log line per file: date, file, what changed.
5. Flag facts two files state differently. Quote both and name both files.
Do not change facts that are not in the files.

(Prompt from stuckwithcopilot.com/guides/copilot-notebook-project/)

Save the results into 02 Wiki and add the lines to 00 Change log. In a notebook, Copilot drafts the pages and a person saves them.

Prompt 3: ask the brain

Using only this notebook, answer: [question]. Name the file for each point.
If it is not in our files, say "Not in our files" and suggest who to ask
from 00 Start here.

(Prompt from stuckwithcopilot.com/guides/copilot-notebook-project/)

Prompt 4: file a good answer back in

Karpathy's method files good answers back into the wiki, so the next question starts from them.

Turn your last answer into a markdown wiki page for 03 Answers.
Title it with the question. Keep every file citation. Add one line
for 00 Change log: date, page name, question answered.
Add nothing that is not in the cited files.

(Prompt from stuckwithcopilot.com/guides/copilot-notebook-project/)

What a good result looks like

Know the limits

Data tip: add only information your company allows in Copilot. Leave out drafts, personal notes and customer personal data. Run the oversharing check before you share.

Make it smarter

Once a month, ask the notebook to list facts two files state differently, wiki pages that cite nothing, and topics in 00 Index with no page. Fix them, then log the fix.

Questions people ask

Cite or share this guide

Build a company second brain in Copilot. Stuck with Copilot. https://stuckwithcopilot.com/guides/copilot-notebook-project/ Last checked Oct 21, 2026.

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Official references

• How Microsoft Copilot Notebooks works
• Add references to your Copilot Notebook
• Copilot Notebooks licensing options
• Share a Copilot Notebook
• Copilot Notebooks now works with Markdown, plain-text, and rich-text files
• Introducing a team knowledge base, curated by Copilot and agents
• Customize how Copilot responds to you
• Copilot personalization and memory
• Copilot Studio quotas and limits

Method and community sources

• Andrej Karpathy, LLM Knowledge Bases (X post)
• Ben Stegink, Intelligink, second brain with LLM wikis and Copilot Cowork
• Andrej Karpathy, llm-wiki idea file (GitHub gist)
• 2toLead summary of the SharePoint team knowledge base
• Power Platform Community: OneNote pages as agent knowledge

Last checked against Microsoft docs: Oct 21, 2026.