google--adk-python/contributing/samples/mcp/mcp_postgres_agent/README.md

PostgreSQL MCP Agent

This agent uses the PostgreSQL MCP server to interact with PostgreSQL databases. It demonstrates how to:

• Connect to a PostgreSQL database using MCP (Model Context Protocol)
• Use uvx to run the MCP server without manual installation
• Pass database credentials securely via environment variables

Prerequisites

• PostgreSQL Database: You need access to a PostgreSQL database with a connection string
• uvx: The agent uses uvx (part of the uv package manager) to run the MCP server

Setup Instructions

1. Configure Database Connection

Create a .env file in the mcp_postgres_agent directory:

POSTGRES_CONNECTION_STRING=postgresql://user:password@host:port/database

Example connection string format:

postgresql://username:password@localhost:5432/mydb
postgresql://postgres.xyz:password@aws-region.pooler.supabase.com:5432/postgres

2. Run the Agent

Start the ADK Web UI from the samples directory:

adk web

The agent will automatically:

• Load the connection string from the .env file
• Use uvx to run the postgres-mcp server with unrestricted access mode
• Connect to your PostgreSQL database

3. Example Queries

Once the agent is running, try these queries:

• "What tables are in the database?"
• "Show me the schema for the users table"
• "Query the first 10 rows from the products table"
• "What indexes exist on the orders table?"
• "Create a new table called test_table with columns id and name"

Configuration Details

The agent uses:

• Model: Gemini 2.0 Flash
• MCP Server: postgres-mcp (via uvx)
• Access Mode: Unrestricted (allows read/write operations). Warning: Using unrestricted mode in a production environment can pose significant security risks. It is recommended to use a more restrictive access mode or configure database user permissions appropriately for production use.
• Connection: StdioConnectionParams with 60-second timeout
• Environment Variable: DATABASE_URI (mapped from POSTGRES_CONNECTION_STRING)

Troubleshooting

• Ensure your POSTGRES_CONNECTION_STRING is correctly formatted
• Verify database credentials and network access
• Check that uv is installed (pip install uv or brew install uv)