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.

Related MCP server: thoughtgraph-mcp

Architecture

How It Works

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

Every tool declares an input schema (validated), an output schema, and behavior annotations (read-only vs. write), and returns machine-readable structuredContent alongside a JSON text block. Writes merge: re-creating an existing node or edge updates the fields you provide and preserves the ones you don't.

The server also exposes MCP prompts — a system prompt with the overall tool-usage workflow, plus per-tool usage guidance under each tool's name.

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

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