Building effective agents Written by Erik Schluntz and Barry Zhang directly from Anthropic, it defines the fundamental distinction between workflows (predefined paths) and agents (LLMs that manage their own processes), and describes the 5 essential orchestration patterns: Prompt Chaining, Routing, Parallelization, Orchestrator-Workers, and Evaluator-Optimizer. The most valuable contribution is the counterintuitive recommendation: avoid unnecessary complexity—simple, compostable systems consistently outperform elaborate frameworks.