A tool is a named, typed function the model may call, described to it by a name, a natural-language description and a JSON schema for its parameters. The description is prompt engineering, not documentation: it is the only thing standing between the model and a plausible misuse.

Tool

A tool surface designed for a programmer exposes primitives; a tool surface designed for an agent exposes intents. Replacing six granular calls with one that expresses what the agent actually wants removes the six ways it could sequence them wrongly.

Write Tools for the Model, Not for the Machine

A tool that returns 'Error 422' teaches the agent nothing. A tool that returns 'since must be an ISO-8601 date; you passed "last week"' turns a dead end into a one-step correction, and is the single highest-leverage change to most tool surfaces.

Returning Errors the Model Can Act On

A topic of the Building AI Agents course. Planned for 2 hours at Medium difficulty.

University of Michigan - Ann Arbor

A category of the Building AI Agents course, covering 4 topics.

Tool Use and Function Calling

Designing Tool Schemas

A topic of the Building AI Agents course. Planned for 1.5 hours at Medium difficulty.

Structured Output and Schema Validation

A topic of the Building AI Agents course. Planned for 2 hours at Hard difficulty.

Failure Handling in the Tool Loop

A topic of the Building AI Agents course. Planned for 1.5 hours at Hard difficulty.

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