📚 Glossary
Tool use (function calling)
In one line: When an AI model can call external functions — search, calculator, database — instead of just generating text.
Tool use (also called function calling) is when an LLM can invoke external functions during a conversation. The model decides which function to call, with what arguments; your code runs the function; the result goes back to the model, which uses it to produce the final answer.
This turns LLMs into agents that can:
- Search the web for current info
- Run calculations precisely (without LLM math errors)
- Query databases
- Send emails or messages
- Control a browser or computer
Both OpenAI and Anthropic support tool use natively. MCP standardises how tools are described to AI clients.
See it in action — ask any AI about tool use (function calling) on AskAI.free.
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