Build Your AI Second Brain with Claude Code

A skill for Claude Code that generates a personalized Product Requirements Document (PRD) for building your own AI second brain - a proactive, persistent AI assistant that knows your context, remembers across sessions, and keeps you informed.

Watch the overview: How I Built My AI Second Brain with Claude Code (YouTube)

What This Does

You fill out a simple requirements template describing your tools, workflow, and preferences. Then Claude Code generates a phased build plan tailored to your setup - covering memory, integrations, skills, a proactive heartbeat, chat interface, and security hardening.

The generated PRD gives you (or your coding agent) a step-by-step blueprint for building a second brain that:

• Remembers across sessions - decisions, preferences, context, all in markdown files
• Connects to your platforms - Gmail, Slack, Calendar, Asana, Linear, GitHub, and more
• Proactively monitors your email, calendar, and tasks every 30 minutes
• Chats with you through Slack (or Discord, or any messaging platform)
• Searches months of memory with hybrid keyword + semantic search
• Drafts replies in your voice using RAG on your past messages
• Tracks habits with daily nudges inspired by Atomic Habits

Quick Start

1. Install the Skill

Copy the .claude/skills/create-second-brain-prd/ directory into your project:

# Clone this repo
git clone https://github.com/coleam00/second-brain-starter.git

# Copy the skill into your project
cp -r second-brain-starter/.claude/skills/create-second-brain-prd \
      your-project/.claude/skills/create-second-brain-prd

Or just copy the .claude/ folder from this repo into an existing project.

2. Fill Out the Requirements Template

Copy the template to your workspace and fill it out:

cp .claude/skills/create-second-brain-prd/my-second-brain-requirements.md \
   ./my-second-brain-requirements.md

The template has 8 sections:

1. About You - Name, role, timezone
2. Your Platforms - Which tools you use (Gmail, Slack, Linear, etc.)
3. Top Tasks - 3-5 things you want AI to handle proactively
4. Proactivity Level - Observer, Advisor, Assistant, or Partner
5. Security Boundaries - What the agent should never do without permission
6. Memory Categories - What types of knowledge matter to you
7. Infrastructure - OS, local vs. VPS deployment
8. Integration Priority - Which 3 integrations to build first

See example-my-second-brain-requirements.md in the skill directory for a completed example.

3. Generate Your PRD

Open Claude Code in your project and run:

/create-second-brain-prd ./my-second-brain-requirements.md

Claude will:

1. Read your requirements
2. Load the architecture reference blueprint
3. Research every tool and API in your stack via web search
4. Generate a personalized 9-phase PRD at .agent/plans/second-brain-prd.md

4. Build It

Follow the phases in your PRD. Each phase includes:

• What to build and why
• Key files to create (with paths)
• Dependencies on previous phases
• Complexity estimate
• Personalization notes based on your answers

The recommended build order:

Phase	What	Complexity
1	Memory Layer (SOUL.md, USER.md, MEMORY.md, daily logs)	Low
2	Hooks (SessionStart, PreCompact, SessionEnd)	Medium
3	Memory Search (hybrid keyword + semantic)	Medium
4	Integrations (your top 3 platforms)	Medium each
5	Skills (vault structure + custom skills)	Low-Medium
6	Proactive Systems (heartbeat + daily reflection)	High
7	Chat Interface (Slack/Discord bot)	High
8	Security Hardening (sanitization, guardrails)	Medium
9	Deployment (local scheduler or VPS)	Medium

Architecture Overview

The second brain is built on Claude Code and the Claude Agent SDK. No massive framework - just markdown files, Python scripts, and an Obsidian vault.

Memory Layer (center of everything)
    SOUL.md - Agent personality, values, boundaries
    USER.md - Your profile, accounts, preferences
    MEMORY.md - Key decisions, lessons, active projects
    daily/YYYY-MM-DD.md - Timestamped session logs

Hooks (context persistence)
    SessionStart - Loads memory into every conversation
    PreCompact - Saves context before auto-compaction
    SessionEnd - Captures decisions on exit

Integrations (platform connections)
    Python CLI wrapper pattern - LLM never sees API keys
    query.py gmail list / query.py asana overdue / etc.

Skills (extensible capabilities)
    Progressive disclosure - metadata always loaded, full instructions on demand

Heartbeat (proactive monitoring)
    Python gathers data -> Claude reasons -> notifications sent
    ~$0.05/run vs $0.38 with MCP tool calls

Memory Search (hybrid RAG)
    FastEmbed (local ONNX) + SQLite/Postgres
    70% vector + 30% keyword = best of both worlds

Proactivity Levels

Your choice in the requirements template shapes the entire system:

Level	What It Does
Observer	Notifications only. Never takes action.
Advisor	Drafts emails/messages for your review. Tracks habits with suggestions.
Assistant	Auto-organizes files, auto-logs decisions. Asks for anything external.
Partner	Sends low-risk messages, completes routine tasks. Asks only for irreversible actions.

Learn More

• Full workshop: Join the Dynamous community for a 4-hour hands-on workshop covering every module
• Claude Agent SDK: Documentation
• Obsidian: obsidian.md