Simple Memory MCP Server

A lightweight Model Context Protocol (MCP) server that provides persistent knowledge graph storage for AI assistants. Enables AI agents to maintain memory across sessions through entity-relationship storage with JSON file persistence.

🚀 Features

• Persistent Memory: Knowledge graph storage with automatic persistence to JSON files
• Entity Management: Create, read, update, and delete entities with typed observations
• Relationship Tracking: Manage relationships between entities with type annotations
• Search Capabilities: Full-text search across entity names, types, and observations
• MCP Compliant: Full Model Context Protocol v2025-06-18 compatibility
• Simple Architecture: Lightweight, single-file implementation with minimal dependencies

📋 Table of Contents

• Installation
• Quick Start
• API Reference
• Configuration
• Testing
• Troubleshooting
• Development

🛠 Installation

Interactive Installation (Recommended)

# Bash installer with interactive configuration
curl -fsSL https://raw.githubusercontent.com/your-username/simple-memory-mcp/main/install.sh | bash

What it does:

• 🔍 Auto-detects your Obsidian vaults
• 📁 Configures custom memory storage location
• ⚙️ Sets up Claude Desktop/Cursor automatically
• 🗂️ Optional Obsidian auto-export configuration

Interactive Setup Flow:

📁 Memory Storage Configuration
Where should memory be stored? [~/.cursor/memory.json]: 

🗂️ Obsidian Integration  
Do you use Obsidian? (y/n) [n]: y

📚 Found Obsidian vaults:
  1. My Knowledge Base (/Users/you/Documents/MyVault)
  2. Work Notes (/Users/you/Desktop/WorkVault)
Choose vault (1-2) or enter custom path [1]: 1

Enable auto-export after entity creation? (y/n) [n]: y
Export format (markdown/dataview/canvas/all) [markdown]: all

Manual Installation

Prerequisites

• Node.js v18.x or higher
• npm or pnpm package manager

Install Dependencies

npm install

Environment Setup

The server automatically saves memory to:

• ~/.cursor/memory.json (default)
• Custom path via MEMORY_PATH environment variable

# Optional: Set custom memory file location
export MEMORY_PATH="/path/to/your/memory/directory"

🚀 Quick Start

1. Start the Server

npm start
# or
node index.js

2. Test with MCP Inspector

# Install and run MCP Inspector
npx @modelcontextprotocol/inspector

# Configure server in Inspector:
# Command: node
# Args: /path/to/your/simple-memory-mcp/index.js

3. Basic Usage Example

// Create entities
await client.callTool({
  name: "create_entities",
  arguments: {
    entities: [{
      name: "john-doe",
      entityType: "person",
      observations: ["Software engineer", "Works remotely", "Enjoys hiking"]
    }]
  }
});

// Create relationships
await client.callTool({
  name: "create_relations",
  arguments: {
    relations: [{
      from: "john-doe",
      to: "acme-corp",
      relationType: "works_for"
    }]
  }
});

// Search entities
await client.callTool({
  name: "search_nodes",
  arguments: {
    query: "engineer"
  }
});

📚 API Reference

Tools Overview

Tool	Description	Input	Output
create_entities	Create multiple entities	{entities: Entity[]}	Created entities
create_relations	Create relationships	{relations: Relation[]}	Created relations
add_observations	Add observations to entities	{observations: Observation[]}	Updated observations
delete_entities	Delete entities and relations	{entityNames: string[]}	Deleted entities
delete_observations	Remove specific observations	{deletions: Deletion[]}	Deleted observations
delete_relations	Remove relationships	{relations: Relation[]}	Deleted relations
read_graph	Get complete knowledge graph	{}	Full graph data
search_nodes	Search entities by query	{query: string}	Matching entities
open_nodes	Get specific entities	{names: string[]}	Requested entities
export_to_obsidian	Export graph to Obsidian vault	{vaultPath: string, format?: string}	Export result

Data Types

Entity

interface Entity {
  name: string;           // Unique identifier
  entityType: string;     // Type classification
  observations: string[]; // Array of observation texts
}

Relation

interface Relation {
  from: string;          // Source entity name
  to: string;            // Target entity name
  relationType: string;  // Relationship type
}

Observation

interface Observation {
  entityName: string;    // Target entity name
  contents: string[];    // New observations to add
}

Deletion

interface Deletion {
  entityName: string;      // Target entity name
  observations: string[];  // Observations to remove
}

Detailed Tool Documentation

create_entities

Creates multiple new entities in the knowledge graph.

Input Schema:

{
  "entities": [
    {
      "name": "entity-name",
      "entityType": "person|organization|concept|etc",
      "observations": ["observation1", "observation2"]
    }
  ]
}

Example:

{
  "entities": [
    {
      "name": "alice-johnson",
      "entityType": "person",
      "observations": ["Data scientist", "PhD in Computer Science", "Lives in San Francisco"]
    },
    {
      "name": "tech-startup-xyz",
      "entityType": "organization", 
      "observations": ["AI/ML company", "Founded in 2023", "Series A funding"]
    }
  ]
}

Response:

[
  {
    "name": "alice-johnson",
    "entityType": "person",
    "observations": ["Data scientist", "PhD in Computer Science", "Lives in San Francisco"]
  }
]

create_relations

Creates relationships between existing entities.

Input Schema:

{
  "relations": [
    {
      "from": "source-entity",
      "to": "target-entity", 
      "relationType": "relationship-type"
    }
  ]
}

Example:

{
  "relations": [
    {
      "from": "alice-johnson",
      "to": "tech-startup-xyz",
      "relationType": "works_for"
    }
  ]
}

search_nodes

Search entities using full-text search across names, types, and observations.

Input Schema:

{
  "query": "search-term"
}

Example:

{
  "query": "data scientist"
}

Response: Array of matching entities with complete data.

read_graph

Returns the complete knowledge graph with all entities and relations.

Input Schema:

{}

Response:

{
  "entities": [
    {
      "name": "alice-johnson",
      "entityType": "person",
      "observations": ["Data scientist", "PhD in Computer Science"]
    }
  ],
  "relations": [
    {
      "from": "alice-johnson",
      "to": "tech-startup-xyz", 
      "relationType": "works_for"
    }
  ]
}

export_to_obsidian

Export the knowledge graph to an Obsidian vault in various formats.

Input Schema:

{
  "vaultPath": "/path/to/obsidian/vault",
  "format": "markdown",
  "autoIndex": true
}

Parameters:

• vaultPath (required): Path to the Obsidian vault directory
• format (optional): Export format - "markdown", "dataview", "canvas", or "all" (default: "markdown")
• autoIndex (optional): Whether to create index files (default: true)

Example:

{
  "vaultPath": "/Users/username/Documents/MyVault",
  "format": "all",
  "autoIndex": true
}

Response:

{
  "success": true,
  "vaultPath": "/Users/username/Documents/MyVault",
  "format": "all",
  "entityCount": 42,
  "relationCount": 18,
  "timestamp": "2024-01-15T10:30:00.000Z"
}

⚙️ Configuration

Environment Variables

Variable	Default	Description
MEMORY_PATH	~/.cursor/memory.json	Custom memory file location
NODE_ENV	development	Runtime environment
OBSIDIAN_AUTO_EXPORT	false	Enable automatic Obsidian export after entity creation
OBSIDIAN_VAULT_PATH	-	Path to Obsidian vault for auto-export
OBSIDIAN_EXPORT_FORMAT	markdown	Export format for auto-export

Memory File Structure

The server persists data in JSON format:

{
  "entities": [
    {
      "name": "entity-name",
      "entityType": "type",
      "observations": ["obs1", "obs2"]
    }
  ],
  "relations": [
    {
      "from": "entity1",
      "to": "entity2",
      "relationType": "relationship"
    }
  ]
}

MCP Client Configuration

For Claude Desktop, add to your MCP settings:

{
  "mcpServers": {
    "simple-memory": {
      "command": "node",
      "args": ["/path/to/simple-memory-mcp/index.js"],
      "env": {
        "MEMORY_PATH": "/custom/path/to/memory/directory"
      }
    }
  }
}

🧪 Testing

Running Tests

# Run comprehensive server test
node test-server.js

Expected Test Output

🧪 Testing Simple Memory MCP Server...
✅ Connected successfully!
✅ Found 9 tools: create_entities, create_relations, ...
✅ All tests passed! Server is working correctly.

Manual Testing with Inspector

1. Start MCP Inspector: npx @modelcontextprotocol/inspector
2. Configure server connection
3. Test each tool with sample data
4. Verify persistence by restarting server

Integration Testing

Test with actual MCP clients:

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

const transport = new StdioClientTransport({
  command: "node",
  args: ["index.js"]
});

const client = new Client({
  name: "test-client",
  version: "1.0.0"
}, {
  capabilities: {}
});

await client.connect(transport);

🔧 Troubleshooting

Common Issues

Server Won't Start

Error: Cannot read properties of undefined (reading 'method')

Solution: Ensure you're using the correct MCP SDK version and schema imports:

import {
  ListToolsRequestSchema,
  CallToolRequestSchema,
  ListPromptsRequestSchema,
  ListResourcesRequestSchema
} from '@modelcontextprotocol/sdk/types.js';

Missing Capabilities Error

Error: Server does not support prompts (required for prompts/list)

Solution: Declare all capabilities in server configuration:

const server = new Server(
  { name: 'simple-memory-mcp', version: '1.1.0' },
  {
    capabilities: {
      tools: {},
      prompts: {},
      resources: {}
    }
  }
);

Memory File Permissions

Error: EACCES: permission denied

Solution: Ensure write permissions to memory directory:

mkdir -p ~/.cursor
chmod 755 ~/.cursor

Tool Not Found

Error: Unknown tool: create_entities

Solution: Verify tool registration matches the schema names exactly.

Debug Mode

Enable detailed logging:

console.error("Debug info:", JSON.stringify(data, null, 2));

Performance Issues

For large knowledge graphs (>10,000 entities):

1. Consider implementing pagination for read_graph
2. Add indexing for search operations
3. Implement lazy loading for entity details

🛠 Development

Project Structure

simple-memory-mcp/
├── index.js              # Main server implementation
├── package.json          # Dependencies and scripts
├── test-server.js        # Comprehensive test suite
├── inspector-config.json # MCP Inspector configuration
├── CLAUDE.md             # AI development protocols
└── README.md             # This documentation

Architecture

graph TD
    A[MCP Client] --> B[StdioServerTransport]
    B --> C[Simple Memory Server]
    C --> D[Entity Manager]
    C --> E[Relation Manager]
    C --> F[Search Engine]
    D --> G[JSON File Storage]
    E --> G
    F --> G

Core Classes

SimpleMemoryServer

Main server class handling:

• Memory persistence (loadMemory(), saveMemory())
• Entity operations (CRUD)
• Relationship management
• Search functionality

Key Methods:

• createEntities(entities) - Batch entity creation
• createRelations(relations) - Relationship creation
• searchNodes(query) - Full-text search
• readGraph() - Complete graph export

Extending the Server

Adding New Tools

1. Define tool schema in tools/list handler
2. Implement logic in tools/call handler
3. Add method to SimpleMemoryServer class
4. Update documentation

Custom Storage Backends

Replace JSON file storage:

class DatabaseMemoryServer extends SimpleMemoryServer {
  async saveMemory() {
    // Custom database implementation
  }
  
  async loadMemory() {
    // Custom database loading
  }
}

Contributing

1. Fork the repository
2. Create feature branch: git checkout -b feature-name
3. Run tests: node test-server.js
4. Commit changes: git commit -m "Description"
5. Push branch: git push origin feature-name
6. Create Pull Request

📄 License

MIT License - see LICENSE file for details.

📚 Additional Documentation

• Complete Documentation Index - All technical documentation
• API Reference - Detailed API documentation with TypeScript interfaces
• Debugging Guide - Comprehensive troubleshooting guide
• Obsidian Integration - Visualization and mindmap setup
• Implementation Guide - Built-in export implementation
• Project Roadmap - Strategic planning and future development

🤝 Support

• Issues: GitHub Issues
• Documentation: MCP Protocol Docs
• Community: MCP Discord

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Built with ❤️ using the Model Context Protocol