Constraining the Agent: What I Learned Wiring MCP Into a Legacy System

An engineer wired an AI coding agent to a legacy PHP app and MySQL database through MCP.

The setup let the agent ground answers in real schema and code, but it also created dangerous write access.

The article argues legacy AI tools need tight controls: a disposable database, least-privilege accounts, separate tool environments, and human review before changes.

The core lesson is that grounding makes agents more useful on old systems, but also raises the operational and security blast radius.