Neo4j

Code style: crackerjack Runtime: oneiric Framework: FastMCP uv Python: 3.13+

MCP server for Neo4j graph database operations.

Version: 0.1.3 Status: Internal Bodai integration component

Quick Links

• Overview
• Capabilities
• Quick Start
• MCP Server Configuration
• Tool Reference
• Configuration
• Development

Quality & CI

Crackerjack is the standard quality-control and CI/CD gate for Neo4j MCP changes. Local verification should mirror the Crackerjack workflow used across the Bodai ecosystem.

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Overview

Neo4j MCP exposes graph database workflows through a FastMCP server. It gives agents a typed interface for Cypher execution, node and relationship management, path discovery, and schema inspection while preserving a narrow database client boundary.

Use this server when an agent needs to query or mutate graph data directly. Keep domain-specific graph policies in the calling system or a higher-level service layer rather than embedding them in generic Neo4j tools.

Capabilities

Implemented tool surface:

• Cypher execution: run parameterized Cypher queries
• Node management: create, retrieve, delete, and search nodes
• Relationship management: create and delete relationships between nodes
• Path discovery: find bounded paths between two nodes
• Schema inspection: retrieve labels, relationship types, indexes, and constraints
• Mock mode: exercise tool behavior without a live Neo4j connection
• HTTP health routes: /health and /healthz for MCP client and process supervision checks

Quick Start

Prerequisites

• Python 3.13+
• UV package manager
• Neo4j server for live access

Local Setup

git clone https://github.com/lesleslie/neo4j-mcp.git
cd neo4j-mcp
uv sync --group dev

Run In Mock Mode

export NEO4J_MCP_MOCK_MODE=true
uv run neo4j-mcp start
uv run neo4j-mcp health

Run With Neo4j

export NEO4J_MCP_URI="bolt://localhost:7687"
export NEO4J_MCP_USER="neo4j"
export NEO4J_MCP_PASSWORD="your-password"
export NEO4J_MCP_DATABASE="neo4j"
uv run neo4j-mcp start

The default HTTP bind is 127.0.0.1:3045.

CLI Commands

The CLI is built with mcp-common and provides the standard lifecycle command surface used by Bodai MCP servers.

uv run neo4j-mcp start      # Start the HTTP MCP server
uv run neo4j-mcp stop       # Stop the managed server process
uv run neo4j-mcp restart    # Restart the managed server process
uv run neo4j-mcp status     # Show process status
uv run neo4j-mcp health     # Run the local health probe

MCP Server Configuration

Claude / Codex Style Configuration

Add the server to an MCP client configuration:

{
  "mcpServers": {
    "neo4j": {
      "command": "uv",
      "args": ["run", "neo4j-mcp", "start"],
      "cwd": "/Users/les/Projects/neo4j-mcp",
      "env": {
        "NEO4J_MCP_URI": "bolt://localhost:7687",
        "NEO4J_MCP_USER": "neo4j",
        "NEO4J_MCP_PASSWORD": "your-password",
        "NEO4J_MCP_DATABASE": "neo4j"
      }
    }
  }
}

For tests or local client wiring, replace live connection values with NEO4J_MCP_MOCK_MODE=true.

Health Checks

curl http://127.0.0.1:3045/health
curl http://127.0.0.1:3045/healthz

Tool Reference

Tool	Purpose	Required Inputs
run_cypher	Execute a Cypher query	query
create_node	Create a node with labels and properties	labels
get_node	Retrieve a node by ID	node_id
delete_node	Delete a node by ID	node_id
find_nodes	Search nodes by labels and properties	none
create_relationship	Create a typed relationship between nodes	type, start_node_id, end_node_id
delete_relationship	Delete a relationship by ID	relationship_id
find_paths	Find paths between two nodes	start_node_id, end_node_id
get_schema	Retrieve database schema details	none

Tool responses follow a consistent ToolResponse shape:

{
  "success": true,
  "message": "Query returned 3 records",
  "data": {},
  "error": null,
  "next_steps": []
}

Configuration

Committed defaults live in settings/neo4j.yaml. Runtime overrides should come from environment variables or a local .env file that is not committed.

Setting	Environment Variable	Default
Neo4j URI	NEO4J_MCP_URI	bolt://localhost:7687
User	NEO4J_MCP_USER	neo4j
Password	NEO4J_MCP_PASSWORD	empty
Database	NEO4J_MCP_DATABASE	neo4j
Max connection lifetime	NEO4J_MCP_MAX_CONNECTION_LIFETIME	3600
Max pool size	NEO4J_MCP_MAX_CONNECTION_POOL_SIZE	50
Connection timeout	NEO4J_MCP_CONNECTION_TIMEOUT	30.0
Mock mode	NEO4J_MCP_MOCK_MODE	false
HTTP host	NEO4J_MCP_HTTP_HOST	127.0.0.1
HTTP port	NEO4J_MCP_HTTP_PORT	3045
Log level	NEO4J_MCP_LOG_LEVEL	INFO
JSON logs	NEO4J_MCP_LOG_JSON	true

Project Structure

neo4j_mcp/
  cli.py                 # mcp-common lifecycle CLI
  client.py              # Neo4j driver boundary
  config.py              # Pydantic settings and logging
  models.py              # Typed graph request and response models
  server.py              # FastMCP application factory
  tools/graph_tools.py   # Registered MCP tools
settings/
  neo4j.yaml             # Committed defaults
tests/

Development

uv sync --group dev
uv run pytest
uv run ruff check neo4j_mcp tests
uv run ruff format neo4j_mcp tests
uv run mypy neo4j_mcp

Use targeted tests when isolating graph behavior:

uv run pytest tests -k graph -v

Security Notes

• Do not commit Neo4j passwords or connection strings containing credentials.
• Prefer parameterized Cypher through params when passing user-controlled values.
• Treat run_cypher as a privileged tool because it can mutate data.
• Use database permissions and separate users to constrain agent-accessible operations.