ReWOO (Reasoning WithOut Observation)

ReWOO is an agent architecture that separates planning from execution. The model produces the full plan up front — including every tool call with placeholder variables for tool outputs — before any tool runs. Tools then execute in sequence or in parallel, and a final solver pass integrates the actual results into the final answer. This removes the interleaved reasoning-action-observation loop that ReAct uses, cutting token cost because the model does not re-read and re-reason over each intermediate observation. The trade-off is adaptivity: if a tool returns something the planner did not anticipate, ReWOO cannot easily change course mid-execution, whereas ReAct can. ReWOO suits well-structured tasks with predictable tool behavior.