What Is Tool Calling? How AI Models Turn Decisions Into Actions
Unite.AI, Friday, October 16th, 2026
A primer on tool calling: schemas, validation, permissions and failure modes in the loop behind AI agents.
The guide explains that tool calling lets a model request a function, API or action with structured arguments, while the application decides whether the call is valid, authorized and executed.
It recommends tool descriptions with clear positive and negative selection criteria, along with narrow JSON Schema definitions to reduce invented parameters.
It also covers modes such as automatic, required and restricted tool selection, and distinguishes tool calling from structured output and from raw APIs.
A core point is that a secure runtime never treats model output as automatically authorized code.