One Iceberg MCP Server, Seven Catalogs: What It Takes to Reach Each One

Step by step: one Python MCP server with four read-only Apache Iceberg tools, pointed at Polaris, BigLake, OneLake, Glue, S3 Tables and Horizon by changing one environment variable. All four tools work on all six. What changes per catalog is the login, the storage package, and one Azure credential that takes 553 seconds.