Function Calling and Tool Schemas

Tool use runs on a function-calling protocol: you declare each tool as a JSON schema, the model returns a structured call (name plus arguments) that your code checks and executes, and the result flows back into the conversation. Design is what's hard, not the wiring: how you write tool descriptions and shape results governs whether the model reaches for the correct tool with correct arguments, and pinning output to a schema can shave a measurable slice off accuracy. Applied-AI interviews test it because schema design is where most agents fail without anyone noticing.