What is tool calling?
Tool calling, also called function calling, is when the model asks a named tool to run, like 'look up the order' or 'draft a calendar hold,' instead of only writing text.
Also called: function calling, tool use
In plain English
The model decides a tool might help, fills in the blanks that tool expects, and your app runs it. You should see the call. A tool that can email or refund is not the same as a tool that can only read. A tool call is a real action with a real side effect, even when the chat looks like talk. Letting the model 'check the calendar' is fine. Letting it 'move the appointment' is a different permission. Name each tool in the SOP the way you would name a key on a ring. If you cannot explain what the tool changes, do not offer it. Log the call. If you cannot see that the calendar was actually opened, you cannot tell a story from a click. Name the tool after the drawer it opens, not after the vendor's marketing. Nickname it on the SOP card. Etch that nickname on the laminated card.
How an owner would use it
Split tools into read and write. Let the agent read the schedule and the SOP. Require a person for send, pay, delete, and anything that changes a customer record.
Common mistakes
Turning on every tool because the menu allows it is how a draft becomes a refund. Function calling is the same idea under another name. The model fills in blanks and your app runs the function. If you cannot name the function in a sentence a new hire would understand, do not enable it. Read tools first. Send, pay, and delete stay off until a person has watched the calls.
A worked example
A neighborhood retailer
Look up the order, do not refund it
This is an illustration, not a customer result. The shop assistant can call a tool that reads an order status. Refunds are a different tool, and it stays off. The model can say 'this order shipped Tuesday' because the tool returned that. It cannot push a refund button.
Related terms
Prompts and guides
Questions owners ask
What is tool calling?
Tool calling is when an AI model invokes a function you defined, such as a lookup or a send, instead of only generating text. Function calling is the same idea.
How do I use tool calling safely?
Allow read tools first. Log every call. Put a human approval on tools that send, pay, or delete.
What happens if the model invents a tool?
A solid setup only runs tools you defined. If the model names a function that does not exist, the call should fail in the log, not guess. That failure is a reason to tighten the instructions, not to add a broader tool.
Product guides are on AI apps for business.