Tool use

Tool use is a system’s ability to invoke an external function, service, interface, or device and incorporate the result.

Plan for this page

Understand one concept in plain language and connect it to nearby ideas.

You will leave with: Tools can search, calculate, read records, send messages, edit files, control software, or act in the physical world. The surrounding system must validate arguments, enforce access, handle errors, and decide whether execution needs approval.
Time: 3–8 min
Before you begin: No prerequisite. Keep one real example in mind.
Do this now: Read the explanation, then compare the example with the common misunderstanding.

Prepared next stepInspect tools and interfaces

Tool useTool use is a system’s ability to invoke an external function, service, interface, or device and incorporate the result.

Agent
Function calling
Permission
API

Plain explanation

Tools can search, calculate, read records, send messages, edit files, control software, or act in the physical world. The surrounding system must validate arguments, enforce access, handle errors, and decide whether execution needs approval.

Example

A model requests a currency-conversion function with an amount and two currencies, then uses the returned rate in its response.

Why it matters

Tools move a system from generating suggestions toward reading or changing an environment. Each tool adds permissions, failure modes, dependencies, and possible consequences.

Common misunderstanding

Misconception: if the model can describe an action, it can safely perform it. Correction: execution requires a real tool, valid authority, checked inputs, and controlled handling of results.

Related concepts

Follow relationships, not only the alphabet

AgentAn AI agent is a system that continues across steps toward a goal and can select or use actions, tools, or information within defined controls.Function callingFunction calling lets a model propose a structured function name and arguments for software to validate and optionally execute.PermissionA permission is an authorized ability to access information, use a tool, or perform an action under defined conditions.APIAn API, or application programming interface, is a defined way for software components to request functions or exchange data.

Inspect tools and interfaces

Sources and scope

What supports this object

Hugging Face Agents Course — IntroductionHugging Face

Illustrates models selecting structured tools and using observations; specific libraries, prompting patterns and tool schemas are not universal.

Open source

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