QRefAI
Contents
Custom AI Agents

Preface — what this series is actually for

3 min · Updated June 2026

For engineers and technical leads who will build, buy, or sign off on agent systems.

What this series is for

Agentic AI is easy to read about and hard to reason about. Benchmarks disagree, ROI figures shift, and “agentic” gets stretched to cover everything from an autonomous planner to a single function call in a loop. Underneath the noise, though, a real engineering discipline is taking shape — and that discipline is what this series is about.

Key Takeaway

Most writing about agentic AI is written to impress, not to inform. This series is built the other way: where evidence is strong it builds on it; where it’s soft or vendor-supplied, it says so plainly.

The goal is to give you a working mental model of how custom AI agents are built and run in production, as the field actually stands in mid-2026.

This is not a tutorial, and you won’t finish it having installed a framework. You will finish it able to look at any agent system — a claims processor, a contract reviewer, a clinical scribe, a customer-service brain — and decompose it into the same handful of moving parts.

What you will be able to do after reading this

Once you can break an agent system into its parts, the tool names stop mattering and the decisions start mattering. The framework you pick matters far less than knowing why context management is the central discipline, when a workflow beats an agent, and what the production envelope really consists of.

By the end you’ll be able to decompose any agent system into its components, make genuine architecture decisions instead of picking from a vendor menu, and tell engineering apart from marketing — a practical skill in a space this noisy.

How to read this series

A few conventions worth knowing up front. Where evidence is strong, this series builds on it; where it’s soft or vendor-supplied, it says so plainly. Real deployments are described as they actually played out, including the parts that were later scaled back. Treat every claim — including the ones here — as something to pressure-test against your own context. That’s not a caveat; it’s how this material is meant to be used.

What this series covers

Eight sections, each built around a question a real practitioner would ask. Read them in order for the full picture, or jump to the one closest to where you are right now — each stands on its own.