MC2DB is a database-native architecture for governing Model Context Protocol (MCP) tool access to enterprise data. The paper argues that MCP should standardize tool discovery and invocation, while database management systems should remain the authoritative control plane for users, roles, privileges, row-level policies, stored procedures, transactions, and audit evidence. It introduces a thin MCP listener, database-resident governance catalog, execution broker, and audit model for making LLM-mediated database access institutionally governable.