What is Tool Use in AI? Function Calling Explained

What is tool use in AI?

Tool use (or function calling) allows LLMs to interact with external systems by generating structured API calls. Instead of just generating text, models like GPT-5 and Claude 4 can search databases, call APIs, execute code, and perform real-world actions.

Common Tool Types

Search: Web search, database queries, RAG retrieval
Code execution: Python interpreters, sandboxed environments
APIs: Weather, calendars, CRMs, payment systems
File operations: Read, write, analyze documents

Tool Use Risks

Hallucinated parameters causing incorrect actions
Prompt injection triggering unauthorized tool calls
Excessive API calls increasing costs
Data exfiltration through tool responses

Monitoring Tool Invocations

Track every tool call for safety:

Log all function names and parameters
Validate parameters before execution
Rate limit sensitive operations
Alert on unusual tool patterns

Why monitor AI tool use?

Tool use amplifies AI risks. A hallucinated function call could delete data, send incorrect emails, or make unauthorized purchases. Monitor tool invocations to catch errors before they cause damage.