Tool loop
The agent picks the next tool from an approved list, reads the result, and repeats until a stop rule fires.
Category
How an agentic system works
Related terms
A tool loop is the pattern in which an agent picks the next tool from an approved list, reads the result, and decides the next step from it, repeating until a stop rule fires.
When it is the right shape
When the next step depends on what the last one returned and cannot be fixed in advance: a vibration trend leads to the maintenance history, which leads to the spare-parts stock, which leads to a draft work order. It is the most flexible pattern and the hardest to bound, so it is used only where the simpler shapes fall short.
What bounds it
An approved tool list with read-only access by default, a cap on rounds, stop conditions checked outside the model, and a record of every call. The agent never adds a tool or a permission to its own list. The maintenance on the bottleneck line use case uses a tool loop that drafts work orders and reserves parts, while a maintenance planner releases every order.
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