Tool Use
Tool use is a model's ability to call external functions, APIs, or services during a response — such as search, a calculator, a database, or code execution — instead of relying only on its own knowledge. The model decides when a tool is needed, invokes it, and incorporates the returned result.
Definition
Tool UseTool use extends a language model beyond text generation by letting it act on the world through defined capabilities. Implemented via function calling, the model emits a structured request, the application executes the tool, and the result is fed back for the model to reason over and respond.
Tool use is what makes agents practical: it lets models fetch live data, perform precise computation, and trigger actions they could never do reliably from parameters alone. It also introduces new safety considerations, since tools can have real side effects and their inputs may carry injected instructions.
Frequently asked questions
What is Tool Use?
Tool use is a model's ability to call external functions, APIs, or services during a response — such as search, a calculator, a database, or code execution — instead of relying only on its own knowledge. The model decides when a tool is needed, invokes it, and incorporates the returned result.
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