"Function calling" and "tool calling" are largely used interchangeably in practice today — "function calling" was the earlier, more common term (a tool call requesting execution of a named function with specific arguments); "tool calling" became the more general umbrella term as the concept expanded beyond simple function invocation.
Where the Terminology Comes From
Historically: "function calling" — the model requests a specific
function be called with specific arguments, similar to a
function call in programming.
More broadly: "tool calling" — encompasses function calling as
one case, but the "tool" framing better fits a wider range of
capabilities some systems support (e.g. built-in tools like
web search or code execution, not just custom user-defined
functions).In most everyday usage and documentation, you'll see both terms used for essentially the same underlying mechanism — don't expect a rigid, universally agreed distinction between them.
The Underlying Mechanism Is the Same
{
"function": "get_weather",
"arguments": {"city": "Delhi", "units": "celsius"}
}
# Whether you call this a "function call" or a "tool call,"
# it's the same request: a named action with structured
# arguments, produced by the model, to be executed by your code.Practical Guidance
When reading a specific provider's documentation, use whichever term that provider uses — don't assume a meaningful technical difference exists just because different providers or resources favor one term over the other. Focus on understanding the actual mechanism (see How Tool Calling Works) rather than the terminology itself.
Practical Use Case
When discussing this concept in an interview or with a team, using "function calling" and "tool calling" interchangeably is generally fine and understood — being precise about the actual mechanism (schema, validation, execution) matters far more than which term you use.
Common Mistakes
- Treating "function calling" and "tool calling" as fundamentally different mechanisms requiring separate understanding — for practical purposes, they describe the same thing
- Getting stuck on terminology precision instead of understanding the actual request/validate/execute/respond flow
Interview Relevance
"Is there a difference between function calling and tool calling?" — largely terminology, not a fundamental technical distinction; a good answer acknowledges both terms refer to essentially the same mechanism in current common usage.
Practice Question
Explain to a colleague, in one or two sentences, why they shouldn't worry about which term — "function calling" or "tool calling" — a piece of documentation uses.