What Is Evaluation?Evaluation Throughout the Lifecycle of an LLMPre-trainingPost-trainingApplicationEvaluation in ApplicationsThe Three Gulfs of LLM Application DevelopmentThe Gulf of Comprehension (Between the Developer and Data)The Gulf of Specification (Between the Developer and the LLM Agent)The Gulf of Generalization (Between the Data and the LLM Agent)Why LLM Agent Evaluation Is ChallengingThe LLM Evaluation Lifecycle: Bridging the Gulfs with EvaluationAnalyzeMeasureImprovePutting It Together