A SAST tool reads your code the way a spell checker reads a document. It follows data from where it enters, like a request parameter, to where it is used, like a database query, and flags paths that look unsafe. Because it needs no running app, it can check every pull request quickly and point to the exact line.
Its strengths are speed and coverage of known patterns. Its limits are real: it produces false positives, it struggles with logic problems such as missing authorization checks, and it cannot see problems that live in configuration or in how services are deployed. A clean report does not mean the app is secure.
For AI-built apps it is a useful safety net, since generated code often repeats insecure patterns. Run it in CI so findings appear before merge, start with the high-severity rules to avoid alert fatigue, and read each finding to decide whether it is real. Pair it with dynamic testing and manual review of login, permissions, and payment flows.