Tool Use

Definition

Tool use means a model calls an external system to perform part of a task.

Simple form:

model -> tool call -> tool result -> model continues

The tool may search, calculate, fetch data, edit files, run code, or perform another operation.

Tool use extends the model's computation beyond text generation.

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Why Tools Are Useful

A model has limits.

It may need:

current information
exact calculation
file access
code execution
database lookup
external action

A tool can provide information or capability the model does not have internally.

Tools connect reasoning to external state and operations.

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Tool Use As State Transition

Tool use changes the computation state.

Example:

before tool:
model has a question

tool call:
search or compute

after tool:
model has new evidence

The tool result becomes part of the next input state.

A tool call is a transition that adds external information or action result.

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Choosing Tools

A reasoning model must decide:

whether to use a tool
which tool to use
what input to send
how to interpret the result
what to do next

This makes tool use part of planning and control.

Tool use requires selecting and integrating external operations.

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Tools Do Not Guarantee Correctness

Tools can help, but errors can still happen.

Examples:

wrong tool choice
bad query
misread result
outdated source
tool failure

The model still needs verification and careful integration.

Tool use increases capability, but it does not remove the need for reasoning discipline.

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Final Summary

• Tool use lets a model call external systems.
• Tools can provide data, calculation, execution, or action.
• Tool results become part of later computation.
• Choosing and interpreting tools is itself a reasoning task.
• Tools improve capability but do not guarantee correctness.