Langgraph-MCP Client for Postgresql Example

Langgraph-MCP Client for Postgresql Example

This repository demonstrates a very low level example of how to interact with an MCP server as a docker image, connected to a PostgreSQL database for LangGraph agents.

model context protocol

MCP is an open protocol that standardizes how applications provide context to LLMs. Think of MCP like a USB-C port for AI applications. Just as USB-C provides a standardized way to connect your devices to various peripherals and accessories, MCP provides a standardized way to connect AI models to different data sources and tools.

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Prerequisites

Before you begin, ensure you have the following installed on your system:

• Docker
• PostgreSQL Database - running and populated
• MCP Servers

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Flow and tools

• We use a postgresql database that the Postgresl MCP Server is aware of through the config
• from langchain_mcp_adapters.tools import load_mcp_tools creates the mcp tool
• create_react_agent is a fast agent templater
• we output the stream to file

Project Setup Instructions

1. Clone the Repository

Clone this repository to your local machine:

git clone https://github.com/your-repo/Langchain-MCP.git
cd Langgraph-mcp-client directory

2. Create a .env File

Create a .env file in the root of the repository with the following variables:

DB_HOST=<your-database-host>
DB_PORT=<your-database-port>
DB_USER=<your-database-username>
DB_PASSWORD=<your-database-password>
DB_NAME=<your-database-name>

Replace the placeholders with your actual database and MCP server connection details.

3. Install UV Package

Install the UV package globally if you haven't already:

Astral uv

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MCP Server Setup

1. Clone the repo MCP Servers to a separate directory
2. Run - docker build -t mcp/postgres -f src/postgres/Dockerfile . to build and tag the image

Usage Instructions

1. Sync the UV Package

Run the following command to sync the UV package:

uv sync

This command ensures that the UV package installs the package correctly.

2. Run the Query Agent

Start the query agent using the following command:

uv run queryagent

This will prompt for the user query

Alt - with query (Banking database)

uv run queryagent "Who holds the most funds in thier account?"

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TODO:

• Output formating
• Multi agent

Troubleshooting

• Database Connection: Verify the .env file contains the correct database credentials.
• UV Package Errors: Ensure the UV CLI is installed globally and the uv sync command completes without errors.

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Contributing

Feel free to open issues or submit pull requests to improve this repository.

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License

This project is licensed under the MIT License. See the LICENSE file for details.