Langgraph-MCP Client for Postgresql Example

What is Langgraph-MCP Client for Postgresql Example?

This repository demonstrates a low-level example of how to interact with an MCP server as a Docker image, connected to a PostgreSQL database for LangGraph agents. It is intended for developers who want to integrate PostgreSQL data sources with LangGraph using the Model Context Protocol (MCP).

How to use Langgraph-MCP Client for Postgresql Example?

Clone the repository, create a .env file with database credentials (DB_HOST, DB_PORT, DB_USER, DB_PASSWORD, DB_NAME), install the UV package globally, and build the MCP Postgres Docker image. Then run uv sync followed by uv run queryagent to start the query agent, optionally passing a natural language query as an argument (e.g., uv run queryagent "Who holds the most funds in their account?").

Key features of Langgraph-MCP Client for Postgresql Example

• Connects to a PostgreSQL database via an MCP server.
• Uses langchain_mcp_adapters.tools.load_mcp_tools to create MCP tools.
• Employs LangGraph's create_react_agent for fast agent templating.
• Outputs the agent’s stream to a file.
• Accepts user queries via command line.

Use cases of Langgraph-MCP Client for Postgresql Example

• Querying a banking database using natural language questions.
• Learning how to integrate a PostgreSQL MCP server with LangGraph agents.
• Prototyping a LangGraph agent that uses database tools over MCP.

FAQ from Langgraph-MCP Client for Postgresql Example

What are the prerequisites for running this project?

You need Docker, a running PostgreSQL database, and the MCP Servers repository (to build the Postgres MCP image). The UV package manager must also be installed globally.

How do I set up the database connection?

Create a .env file in the repository root with the variables DB_HOST, DB_PORT, DB_USER, DB_PASSWORD, and DB_NAME, replacing placeholders with your actual credentials.

What should I do if I encounter UV package errors?

Ensure the UV CLI is installed globally and that the uv sync command completes without errors.

How do I build the PostgreSQL MCP Server Docker image?

Clone the MCP Servers repository, navigate to its directory, and run docker build -t mcp/postgres -f src/postgres/Dockerfile .

How can I run the query agent with a specific question?

Run uv run queryagent "your question" from the project directory, replacing "your question" with the desired natural language query.