The New Relic CLI tool is an open-sourced command line interface developed by IBM that allows users to manage New Relic resources, such as Synthetics monitors, Alerts policies and conditions, user accounts, and Insights dashboards. It provides features like creating, editing, and deleting resources, backing up and restoring configuration data, and automating tasks with CI/CD processes. The tool is designed to help teams increase their deployment speed and cadence by reducing the burden of managing boilerplate code. Users can use the CLI to manage these resources, create daily backups of Synthetics monitors, save New Relic settings to source-control tools, and configure retries and return codes for automation purposes.