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n. / Agents and tools
ReAct pattern
Definition
ReAct, short for reason and act, is an agent pattern in which the model alternates between writing a short thought about what to do and taking an action with a tool, then reads the observation before the next thought.
In more detail
It was an early, influential recipe for tool-using agents and still underlies many frameworks, though modern models usually do the reasoning internally or through native tool calling. Seeing the thought, action and observation of each cycle in a trace makes it easy to find the step where the reasoning went off course.
Example
Thought: I need the order status. Action: lookup_order(A-1042). Observation: shipped on Monday. Thought: I can answer now.
Related terms
