Comparison
Function Calling vs Tool Use
Function Calling and Tool Use are both common AI/LLM terms but cover different ideas. Here is a quick side-by-side.
When you would reach for Function Calling
Function Calling comes up when the question is fundamentally about agents & tools.
OpenAI's tools parameter and tool_calls response.
When you would reach for Tool Use
Tool Use comes up when the question is fundamentally about agents & tools.
Calling get_weather(city) and getting back JSON the model interprets.
Frequently asked
What is the difference between Function Calling and Tool Use?
Function Calling: Function calling is the specific API mechanism by which an LLM emits a structured request to invoke a named function with typed arguments. The OpenAI-popularized way to do tool use. Tool Use: Tool use is when an LLM can call external functions — APIs, code interpreters, databases, web fetchers — and read their results. The mechanism that turns chat into action.
When should I use Function Calling vs Tool Use?
Function Calling is the right concept when you are focused on agents & tools. Tool Use applies when you are focused on agents & tools.
Are Function Calling and Tool Use the same thing?
No. Function Calling is agents & tools; Tool Use is agents & tools. They are related but address different parts of the AI stack.