Manual ReAct Trace: Walking Through One Query Step by Step
~20 min read
Running the ReAct loop manually — calling the agent, reading its Thought/Action output, executing the tool yourself, and feeding back the Observation — builds full visibility into how the loop actually behaves before automating any of it.
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Key points
- •Running the loop manually first gives full visibility into the agent's reasoning before trusting an automated controller
- •A blank ('') message tells the agent to continue reasoning from wherever it paused, without adding a new user question
- •The human plays the role of the controller in this manual version — actually calling the tool function and formatting the result as 'Observation: ...'
- •The Observation message must match the exact format the system prompt led the model to expect
- •This step-by-step trace is what the automated agent_loop() (next subtopic) replaces with code — same mechanics, no human in the loop