gem-hunter

A Model Context Protocol (MCP) server that provides both HTTP and Stdio transports for interacting with PostgreSQL databases. This server exposes database resources and tools through both transport methods, allowing for flexible integration in different environments.

• Dual Transport Support: Both HTTP (StreamableHTTPServerTransport) and Stdio (StdioServerTransport)
• Database Resources: List tables and retrieve schema information
• Query Tool: Execute read-only SQL queries
• Stateful Sessions: HTTP transport supports session management
• Docker Support: Containerized deployments for both transports
• Production Ready: Graceful shutdown, error handling, and logging

The database credentials must be passed as:

1. Either environment variables

# PostgreSQL Database Connection String
export POSTGRES_URL=your_connection_string

# PostgreSQL Database Configuration if POSTGRES_URL is not provided
export POSTGRES_USERNAME=your_username
export POSTGRES_PASSWORD=your_password
export POSTGRES_HOST=localhost
export POSTGRES_PORT=5432 # this is the default
export POSTGRES_DATABASE=your_database

# HTTP Server Configuration
# Following are the default values
export PORT=3000
export HOST=0.0.0.0

# CORS Configuration (comma-separated list of allowed origins)
# Following are the default values
export CORS_ORIGIN=http://localhost:8080,http://localhost:3000

# Environment
# Following are the default values
export NODE_ENV=development

2. Or in the working directory (directory where npx command will be run): create a .env file (the package uses dotenv package)

# .env.example
# PostgreSQL Database Configuration
POSTGRES_USERNAME=your_username
POSTGRES_PASSWORD=your_password
POSTGRES_HOST=localhost
POSTGRES_DATABASE=your_database

# HTTP Server Configuration
PORT=3000
HOST=0.0.0.0

# CORS Configuration (comma-separated list of allowed origins)
CORS_ORIGIN=http://localhost:8080,http://localhost:3000

# Environment
NODE_ENV=development

1. Download node.js and npm from here
2. Run the package. By default, it will run streamable http on port 3000:

npx @ahmedmustahid/postgres-mcp-server
# or npx @ahmedmustahid/postgres-mcp-server --port 3000 --verbose

3. For stdio transport:

npx @ahmedmustahid/postgres-mcp-server stdio
# npx @ahmedmustahid/postgres-mcp-server stdio --verbose

Copy environment template

cp .env.example .env

Edit your database credentials

nano .env

1. Install podman from here
2. Install uv from here
3. Install podman compose package: uv add podman-compose (or uv sync to sync packages in pyproject.toml)

#get the environment variables
set -a
source .env
set +a
podman machine start
make podman-up

First, install node.js and npm, build the project following the above instructions. Edit your claude_desktop_config.json

{
  "mcpServers": {
    "postgres-mcp-server": {
      "command": "npx",
      "args": [
        "@ahmedmustahid/postgres-mcp-server",
        "stdio"
      ],
      "env": {
        "POSTGRES_USERNAME": "your-username",
        "POSTGRES_PASSWORD": "your-password",
        "POSTGRES_HOST": "hostname",
        "POSTGRES_DATABASE": "database-name"
      }
    }
  }
}

Verify from Claude Desktop Window

Prompt: Show sales table from last year.

First, install node.js and npm, build the project following the above instructions. Install MCP Inspector: instructions: here

npx @modelcontextprotocol/inspector npx @ahmedmustahid/postgres-mcp-server stdio

First, run the server (shell where environment has been configured):

npx @ahmedmustahid/postgres-mcp-server

Run the mcp inspector from another terminal

npx @modelcontextprotocol/inspector

After selecting Streamable HTTP from drop down menu, insert http://localhost:3000/mcp(default) into URL.

MCP tools:

MCP Resource:

You have to specify these inside the .env file.

A simple greeting message for testing.

Lists all tables in the public schema with their schema URIs.

Returns column information for a specific table.

Execute read-only SQL queries against the database.

Parameters:

• sql (string): The SQL query to execute

The HTTP server includes a basic health check endpoint accessible at the /health endpoint with a GET request (returns 405 Method Not Allowed, confirming the server is responsive).

1. Database Connection Errors

   # Check your database credentials in .env
   # Ensure PostgreSQL is running and accessible

2. Port Already in Use

   # Change PORT in .env or stop conflicting services
   lsof -i :3000

3. Docker Build Issues

   # Clean Docker cache
   npm run docker:clean
   docker system prune -a

4. Session Management (HTTP)

   # Sessions are stored in memory and will reset on server restart
   # For production, consider implementing persistent session storage

1. Create a new file in src/resources/
2. Implement the resource registration function
3. Add it to src/server/server.ts

1. Create a new file in src/tools/
2. Implement the tool registration function
3. Add it to src/server/server.ts

MIT

Please read the contributing guidelines and submit pull requests to the main repository.