AI agent observability is crucial for managing and optimizing costs in large language model (LLM)-based systems, where hidden expenses can arise from various sources such as token usage, context management, multi-step workflows, and external API calls. This concept ensures visibility into every request, decision, and interaction by tracking detailed metrics like token consumption, tool call frequencies, context window sizes, and retry rates, which helps identify costly patterns and inefficiencies. By deploying observability tools, teams can convert opaque billing surprises into clear optimization opportunities, allowing them to implement strategies that reduce costs without sacrificing performance, such as right-sizing models, engineering efficient prompts, and using caching. Real-time cost mapping and anomaly detection further enable proactive management by alerting teams to potential budget overruns, while continuous monitoring and analysis facilitate ongoing improvements and cost savings. Platforms like Galileo enhance this process by integrating observability directly into development workflows, offering automated quality guards, multi-dimensional evaluations, and real-time protection, ultimately ensuring that AI agents operate efficiently and within budget.