Agents · Fast-moving · Intermediate

Tool Use

Letting a model invoke external functions, APIs or code so it can act and fetch facts instead of guessing.

What Tool Use is

Tool use fixes the things language models are structurally bad at: arithmetic, current data, and changing the state of another system.

How it works

Tools are described with names, purposes and typed parameter schemas. The model chooses a tool and emits arguments; the runtime validates and executes them, then returns the result for the next reasoning step.

Why it matters

It is the single largest reliability upgrade available for assistants, because verified computation replaces plausible invention.

Common uses

→Calculators and unit conversion
→Live search and data lookup
→Database and CRM actions
→Code execution and file operations

Strengths

✓Exact results from real systems
✓Extends capability without retraining

Watch for

✓Every tool is an attack surface
✓Poor tool descriptions cause wrong calls

Continue exploring

Function Calling Model Context Protocol Structured Output Prompt Injection