PostgreSQL MCP Server

# CLAUDE.md This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository. ## Overview This is a Model Context Protocol (MCP) server that provides read-only access to PostgreSQL databases. It allows LLMs to inspect database schemas and execute read-only SQL queries. ## Commands ```bash # Install dependencies pnpm install # Build TypeScript to dist/ pnpm run build # Watch mode for development pnpm run watch # Build Docker image (run from repo root) docker build -t mcp/postgres -f src/postgres/Dockerfile . # Run the server (requires database URL argument) node dist/index.js postgresql://localhost:5432/mydb ``` ## Architecture Single-file MCP server (`index.ts`) that: 1. **Resources**: Exposes table schemas from `information_schema.columns` as JSON resources at `postgres://<host>/<table>/schema` 2. **Tools**: Provides a `query` tool that executes SQL within `READ ONLY` transactions (always rolled back) 3. **Transport**: Uses stdio transport for MCP communication The server uses `pg.Pool` for connection management. All queries are intrinsically read-only via PostgreSQL's `BEGIN TRANSACTION READ ONLY`. ## Key Dependencies - `@modelcontextprotocol/sdk`: MCP server implementation - `pg`: PostgreSQL client ## Docker Notes When connecting to PostgreSQL on the host machine from Docker, use `host.docker.internal` instead of `localhost` in the connection URL.