USB-C for Agents

The agent is only as good as its tools.

You ship production systems. You're new to agents. And the agent that aced every demo just went live and called the refund tool with a customer's order ID in the amount field. It passes garbage arguments, loops forever on an error it can't read, and burns ten thousand tokens to do what one function should have handled. You blame the model. It isn't the model.

A huge fraction of agent quality lives in the layer most engineers treat as plumbing: the tools you expose and the way you describe them. Get that layer right and an "average" model becomes a reliable agent. Get it wrong and no frontier model will save you.

This hands-on flagship teaches you to build that layer. You will learn how function calling actually works, why MCP won as the open standard, and why a tool description is a user interface that happens to be read by a model. You will design tools for loops, retries, and honest error feedback; run code execution in a sandbox to cut token costs by orders of magnitude on measured workloads; and ship audit trails, provenance, and an autonomy slider that earns trust. You will face the real tradeoff head-on: every guardrail you add to make a tool safe also narrows what the agent may do alone.

Written by an engineer learning this frontier in the open against retail-scale systems, APIs, and messy data, it turns integration from afterthought into your unfair advantage. Stop tuning prompts. Start engineering the connection. Build agents that work on the first call.

Read chapter one free with Look Inside.

Part of the Build Agents You Can Trust series, in The Verifier's Library.