Gemini API in Ruby: Building AI Agents Without an SDK

Building a production-ready Gemini agent in Ruby means owning the HTTP client, response parsing, tool registry, and state persistence yourself since there's no official SDK. The Interactions API is the right primitive — it tracks full turn history via server-side IDs, supports background execution, and exposes step-level tool calls. This guide covers the full stack: Faraday client setup, tool declaration design, authorization, streaming, and observability.