Democratizing Internal Data — Building an MCP Server That Lets You Search 991 Tables in Natural Language

Hi, I'm Ryan Tsuji , CTO at airCloset — Japan's leading fashion rental subscription service. Today I want to share something I'm genuinely proud of: DB Graph and DB Graph MCP — a Model Context Protocol (MCP) server that lets anyone in our company search and query 15 schemas, 991 tables, 11 SQL databases, and 6 MongoDB instances using natural language through Claude Code. You don't need to know a single table name. Ask "find tables related to returns" and it gives you the answer — across schemas, across database engines. And yes, it can query production data safely. In this post, I'll walk through everything: what it does, how it works, the tool design, actual response formats, how we built the graph, how we operate it, and how we handle permissions and security. The Problem: Nobody Knows All 991 Tables airCloset has been running since 2015 — that's 10 years of accumulated database schema. Resource Count SQL Databases 11 (MySQL 8 + PostgreSQL 3) MongoDB Databases 6 (DocumentDB 5 + Atlas