Designing a Human-Friendly CLI for API-Driven Infrastructure

As Bloomberg’s infrastructure grows and evolves, the tools we use to manage it are becoming increasingly important. To streamline infrastructure management, our team set out to design a REST API and constituent CLI (Command Line Interface) that would comprise a single interface for both programmatic and human interaction with our infrastructure. Traditionally, building a CLI that is tightly coupled to an API requires maintaining a separate codebase, which is tedious and error-prone. Instead, we designed a CLI that dynamically generates commands based on the OpenAPI JSON documentation. However, since APIs are designed for computer interaction, we designed our API to include the information needed to implement a human-friendly CLI. Leveraging Python, FastAPI, and numerous other open source projects, we built a stable, extensible tool that greatly improves how we interact with our infrastructure.