Glossary
Function calling / tool use
Letting a model invoke defined functions with structured arguments.
What it is
Function calling lets an LLM return a structured request to run a defined tool (search, database query, API call). It's the mechanism that turns a chat model into an agent that can act.
Why it matters in production
This is the bridge from text to action. The production rules: strict schemas for every tool, validate arguments before executing anything with side effects, and keep tools narrow and composable rather than one god-tool.
In practice
The model returns {name: 'get_order', arguments: {order_id: 'A-1042'}}; your code validates the id, runs the lookup, and returns the result as an observation.
Related terms
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