Tool Use & Function Calling
How a model reaches outside its own context, and why the tool surface is the part you actually design.
6 topics
What Function Calling Actually Is
The model never calls anything — it emits a structured request naming a tool and its arguments, and your code decides whether to honour it.
core20 minDesigning Tool Schemas
The description and schema are the prompt for that tool — most tool misuse is a specification bug, not a model failure.
core20 minParallel & Sequential Tool Calls
A model can request several tools in one turn — running them concurrently is free latency, and getting the message shape wrong quietly teaches it to stop.
core15 minTool Errors & Recovery
An error result is a prompt — how you word a failure decides whether the model fixes its call, gives up, or loops forever.
core15 minServer-Side vs Client-Side Tools
Some tools run on the provider's infrastructure and return results inside the same response; the rest run on yours — and the split decides who holds the credentials.
deep15 minTools vs Structured Outputs
Both constrain the model to a JSON schema — pick by intent: return me a value, or go do a thing.
core15 min