Private Journal MCP Server

A comprehensive MCP (Model Context Protocol) server that provides Claude with private journaling and semantic search capabilities for processing thoughts, feelings, and insights.

Features

Journaling

• Multi-section journaling: Separate categories for feelings, project notes, user context, technical insights, and world knowledge
• Dual storage: Project notes stay with projects, personal thoughts in user home directory
• Timestamped entries: Each entry automatically dated with microsecond precision
• YAML frontmatter: Structured metadata for each entry

Search & Discovery

• Semantic search: Natural language queries using local AI embeddings
• Vector similarity: Find conceptually related entries, not just keyword matches
• Local AI processing: Uses @xenova/transformers - no external API calls required
• Automatic indexing: Embeddings generated for all entries on startup and ongoing

Privacy & Performance

• Completely private: All processing happens locally, no data leaves your machine
• Fast operation: Optimized file structure and in-memory similarity calculations
• Robust fallbacks: Intelligent path resolution across platforms

Tech Stack

Core Technologies

• Node.js 18+ - Runtime environment with modern JavaScript features
• TypeScript 5.0+ - Type-safe development with strict configuration
• MCP SDK 0.4.0 - Official Model Context Protocol implementation
• @xenova/transformers - Local AI models for semantic embeddings (no external APIs)

AI & Search

• Semantic Embeddings - Multiple model options (MiniLM, DistilRoBERTa, MPNet)
• Vector Similarity - Local cosine similarity calculations
• Natural Language Search - Query understanding without external services

Development & Quality

• Jest - Comprehensive testing framework with mocks
• Biome - Modern linting and formatting
• Oxlint - Additional code quality checks
• GitHub Actions - Continuous integration and testing

Storage & Architecture

• Markdown + YAML - Human-readable entries with structured metadata
• Hierarchical File System - Date-based organization with microsecond precision
• Cross-Platform - Windows, macOS, and Linux support

For detailed architectural decisions, see ARCHITECTURE.md.

Installation

npm install -g private-journal-mcp

Or install locally:

npm install private-journal-mcp

Usage

Basic Usage

private-journal-mcp

This creates journal entries in .private-journal/ in the current working directory.

Custom Journal Path

private-journal-mcp --journal-path /path/to/my/journal

Embedding Model Configuration

You can customize the AI model used for generating semantic embeddings:

export JOURNAL_EMBEDDING_MODEL="Xenova/all-distilroberta-v1"

Available Models:

• Xenova/all-MiniLM-L6-v2 (default) - Fast, 384 dimensions, good general performance
• Xenova/all-distilroberta-v1 - Larger, 768 dimensions, better accuracy
• Xenova/paraphrase-MiniLM-L6-v2 - Optimized for paraphrase detection
• Xenova/all-mpnet-base-v2 - High quality, 768 dimensions, slower but more accurate

The embedding model affects:

• Local search quality - More sophisticated models provide better semantic understanding
• Vector dimensions - Impacts remote server storage and search capabilities
• Processing speed - Larger models are slower but more accurate
• Memory usage - Bigger models require more RAM

Remote Server Integration

To enable optional remote posting of journal entries to a team server, set these environment variables:

export REMOTE_JOURNAL_SERVER_URL="https://api.yourteam.com"
export REMOTE_JOURNAL_TEAMID="your-team-id"
export REMOTE_JOURNAL_APIKEY="your-api-key"

When configured, journal entries will be posted to your remote server in addition to being saved locally. Local journaling always takes priority - if the remote posting fails, the local entry is still saved.

Remote-Only Mode

For teams using a backend server as the single source of truth, enable remote-only mode to skip local file storage entirely:

export REMOTE_JOURNAL_ONLY="true"

In remote-only mode:

• No local storage - entries go directly to the backend server
• Server-side search - all search queries use the backend API
• Error handling - journal operations fail if server is unavailable
• Team collaboration - automatic sharing across team members
• Centralized AI - semantic search powered by backend infrastructure

Remote Payload Format

The server sends JSON payloads with this structure:

For simple entries:

{
  "team_id": "your-team-id",
  "timestamp": 1717160645123,
  "content": "Journal entry text",
  "embedding": [0.1, 0.2, 0.3, 0.4, 0.5, "..."]
}

For structured thoughts:

{
  "team_id": "your-team-id",
  "timestamp": 1717160645123,
  "sections": {
    "feelings": "I feel great about this feature",
    "project_notes": "Architecture is solid",
    "technical_insights": "TypeScript provides great type safety",
    "user_context": "Harper prefers concise responses",
    "world_knowledge": "Semantic search is powerful"
  },
  "embedding": [0.1, 0.2, 0.3, 0.4, 0.5, "..."]
}

Embedding Vectors

Each journal entry includes a semantic embedding vector generated using local AI models (@xenova/transformers). These vectors enable:

• Semantic search on the remote server
• Similarity matching across team entries
• Content clustering and analysis
• AI-powered insights without exposing raw content

The embedding is a numeric array representing the semantic meaning of the journal entry content. Vector dimensions depend on the model used (typically 384 or 512 dimensions).

The remote server should expect POST requests to /journal/entries with x-api-key and x-team-id headers.

Claude Code Plugin

This repository is configured as a Claude Code Plugin. To use it:

Quick Install (Recommended)

claude mcp add-json private-journal '{"type":"stdio","command":"npx","args":["github:2389-research/journal-mcp"]}' -s user

Or install directly from GitHub:

claude mcp install github:2389-research/journal-mcp

What's Included

The plugin provides:

• Tools: process_thoughts, search_journal, read_journal_entry, list_recent_entries
• Resources: Access to journal entries as discoverable resources
• Prompts: Guided templates for daily reflection, project retrospectives, and learning capture

MCP Configuration (Other Clients)

Manual Configuration

For Claude Desktop or other MCP clients, add to your MCP settings:

{
  "mcpServers": {
    "private-journal": {
      "command": "npx",
      "args": ["github:2389-research/journal-mcp"]
    }
  }
}

The server will automatically find a suitable location for the journal files.

MCP Tools

The server provides comprehensive journaling and search capabilities:

process_thoughts

Multi-section private journaling with these optional categories:

• feelings: Private emotional processing space
• project_notes: Technical insights specific to current project
• user_context: Notes about collaborating with humans
• technical_insights: General software engineering learnings
• world_knowledge: Domain knowledge and interesting discoveries

search_journal

Semantic search across all journal entries:

• query (required): Natural language search query
• limit: Maximum results (default: 10)
• type: Search scope - 'project', 'user', or 'both' (default: 'both')
• sections: Filter by specific categories

read_journal_entry

Read full content of specific entries:

• path (required): File path from search results

list_recent_entries

Browse recent entries chronologically:

• limit: Maximum entries (default: 10)
• type: Entry scope - 'project', 'user', or 'both' (default: 'both')
• days: Days back to search (default: 30)

File Structure

Project Journal (per project)

.private-journal/
├── 2025-05-31/
│   ├── 14-30-45-123456.md          # Project notes entry
│   ├── 14-30-45-123456.embedding   # Search index
│   └── ...

User Journal (global)

~/.private-journal/
├── 2025-05-31/
│   ├── 14-32-15-789012.md          # Personal thoughts entry
│   ├── 14-32-15-789012.embedding   # Search index
│   └── ...

Entry Format

Each markdown file contains YAML frontmatter and structured sections:

---
title: "2:30:45 PM - May 31, 2025"
date: 2025-05-31T14:30:45.123Z
timestamp: 1717160645123
---

## Feelings

I'm excited about this new search feature...

## Technical Insights

Vector embeddings provide semantic understanding...

Development

Building

npm run build

Testing

npm test

Development Mode

npm run dev

Improving Claude's Performance

To help Claude learn and improve over time, consider adding journal usage guidance to your ~/.claude/CLAUDE.md file:

## Learning and Memory Management

- YOU MUST use the journal tool frequently to capture technical insights, failed approaches, and user preferences
- Before starting complex tasks, search the journal for relevant past experiences and lessons learned
- Document architectural decisions and their outcomes for future reference
- Track patterns in user feedback to improve collaboration over time
- When you notice something that should be fixed but is unrelated to your current task, document it in your journal rather than fixing it immediately

This enables Claude to build persistent memory across conversations, leading to better engineering decisions and collaboration patterns.

Documentation

Comprehensive Guides

• Architecture & Design Decisions - Technical architecture, design patterns, and key decisions
• Contributing Guidelines - Development setup, code style, testing, and contribution process
• Roadmap & Development Priorities - Current status, planned features, and future direction

API Reference

• docs/spec.md - Original MCP server specification
• docs/backend-api-spec.md - Remote server API documentation
• docs/implementation-plan.md - Development history and implementation details

Getting Help

• Issues: GitHub Issues for bugs and feature requests
• Discussions: GitHub Discussions for questions and community chat
• MCP Protocol: Model Context Protocol Documentation

Author

Jesse Vincent [email protected]

Read more about the motivation and design in the blog post.

License

MIT