sentinel is an open-source CLI + GitHub Action that scans MCP server configurations, live endpoints, and Docker containers for security misconfigurations. It runs 26 detection rules across 3 modules CFG (static config analysis), PRB (live probe), CTR (container inspection) — and outputs in terminal, JSON, SARIF, or HTML. It grew out of our work building Helixar, an AI-native endpoint and API security platform. We kept finding the same MCP misconfigs (no auth, wildcard CORS, plaintext secrets) and wanted a lightweight, composable scanner that CI pipelines could actually use.