MCP Engram — Cognitive Knowledge Graph

A Model Context Protocol (MCP) server for building and exploring a cognitive neuroscience-inspired knowledge graph. Models thought, emotion, reasoning, and episodic memory after the structure of the human mind. Backed by SQLite — zero infrastructure, single file on disk, works offline.

Quick Start

npx mcp-engram

Or install globally:

npm install -g mcp-engram
mcp-engram

The server stores its database at ~/.mcp-engram/knowledge.db by default. No external services required.

Architecture

How It Works

The MCP server exposes 8 tools that let an LLM build, search, and traverse a knowledge graph:

| Tool | Purpose | |---|---| | search_nodes | Full-text search across all nodes (FTS5) | | explore_context | Weighted graph traversal around given nodes | | create_nodes | Create or upsert nodes of any type | | create_relations | Create edges with context, weight, and confidence | | add_sources | Record provenance (Source nodes + DERIVED_FROM links) | | get_temporal_sequence | Follow chronological chains (NEXT, BEFORE, CAUSES) | | create_reasoning_chain | Build structured multi-step reasoning | | get_reasoning_chain | Retrieve reasoning chains by name or topic |

Node Types (15)

Entity, Event, Concept, Attribute, Proposition, Emotion, Agent, ScientificInsight, Law, Location, Thought, ReasoningChain, ReasoningStep, Source, EmotionalEvent

Storage

• SQLite with WAL mode for concurrent reads
• FTS5 virtual table for full-text search with BM25 ranking
• Recursive CTEs for graph traversal
• Single nodes table for all types, edges table with UNIQUE constraint, plus aliases and observations tables
• Complex objects stored as JSON in a properties column

Installation

Prerequisites

• Node.js v18+
• A C/C++ toolchain for compiling the better-sqlite3 native module:
  • Mac: Xcode Command Line Tools (xcode-select --install)
  • Linux: build-essential (apt install build-essential)
  • Windows: Visual Studio Build Tools

From npm

npx mcp-engram

From source

npm install
npx nx build mcp-engram
node dist/servers/mcp-engram/main.js

Environment Variables

| Variable | Required | Default | Description | |---|---|---|---| | MCP_ENGRAM_DB_PATH | No | ~/.mcp-engram/knowledge.db | Path to the SQLite database file |

Integrating with Claude Desktop

Add the server to your Claude Desktop config:

1. Open your config file:

   • Mac: ~/Library/Application Support/Claude/claude_desktop_config.json
   • Windows: %APPDATA%\Claude\claude_desktop_config.json
   • Linux: ~/.config/Claude/claude_desktop_config.json

2. Add the server configuration:

{
  "mcpServers": {
    "mcp-engram": {
      "command": "npx",
      "args": ["mcp-engram"]
    }
  }
}

3. Restart Claude Desktop.

Project Structure

servers/mcp-engram/          # MCP server (TypeScript, ESM)
  src/main/                  # Server bootstrap, tool handlers, prompts
  src/storage/               # SQLite backend, FTS, schema, validation
  src/types/                 # TypeScript interfaces and enums

libs/graphrag-memory/        # Shared type library (Entity, Relation, etc.)

Development

# Build all projects
npx nx run-many -t build

# Test all projects
npx nx run-many -t test

# Lint
npx nx lint mcp-engram

# Build specific project
npx nx build mcp-engram
npx nx build graphrag-memory

License

MIT