Simple PostgreSQL MCP Server

This is a template project for those looking to build their own MCP servers. I designed it to be dead simple to understand and adapt - the code is straightforward with MCP docs attached so you can quickly get up to speed.

What is MCP?

TL;DR - It's a way to write plugins for AI

Model Context Protocol (MCP) is a standard way for LLMs to interact with external tools and data. In a nutshell:

- Tools allow the LLM to execute commands (like running a database query)
- Resources are data you can attach to conversations (like attaching a file to a prompt)
- Prompts are templates that generate consistent LLM instructions

Features

This PostgreSQL MCP server implements:

1. Tools
- execute_query - Run SQL queries against your database
- test_connection - Verify the database connection is working

2. Resources
- db://tables - List of all tables in the schema
- db://tables/{table_name} - Schema information for a specific table
- db://schema - Complete schema information for all tables in the database

3. Prompts
- Query generation templates
- Analytical query builders
- Based on the templates in this repo

Prerequisites

- Python 3.8+
- uv - Modern Python package manager and installer
- npx (included with Node.js)
- PostgreSQL database you can connect to

Quick Setup

1. Create a virtual environment and install dependencies:

   # Create a virtual environment with uv

   uv venv

   

   # Activate the virtual environment

   source .venv/bin/activate  # On Windows: .venv\Scripts\activate

   

   # Install dependencies

   uv pip install -r requirements.txt

   

2. Run the server with the MCP Inspector:

   # Replace with YOUR actual database credentials

   npx @modelcontextprotocol/inspector uv --directory . run postgres -e DSN=postgresql://username:password@hostname:port/database -e SCHEMA=public

   

> Note: If this is your first time running npx, you'll be prompted to approve the installation. Type 'y' to proceed.

After running this command, you'll see the MCP Inspector interface launched in your browser. You should see a message like:

   MCP Inspector is up and running at http://localhost:5173

   

If the browser doesn't open automatically, copy and paste the URL into your browser. You should see something like this:

3. Using the Inspector:
- Click the "Connect" button in the interface (unless there's an error message in the console on the bottom left)
- Explore the "Tools", "Resources", and "Prompts" tabs to see available functionality
- Try clicking on listed commands or typing resource names to retrieve resources and prompts
- The interface allows you to test queries and see how the MCP server responds

4. Take a look at the official docs

Official server developers guide: https://modelcontextprotocol.io/quickstart/server

More on the inspector: https://modelcontextprotocol.io/docs/tools/inspector

Connect Your AI Tool to the Server

You can configure the MCP server for your AI assistant by creating an MCP configuration file:

{
   "mcpServers": {
      "postgres": {
         "command": "/path/to/uv",
         "args": [
            "--directory",
            "/path/to/simple-psql-mcp",
            "run",
            "postgres"
         ],
         "env": {
            "DSN": "postgresql://username:password@localhost:5432/my-db",
            "SCHEMA": "public"
         }
      }
   }
}

Alternatively, you can generate this config file using the included script:

```bash