How to design an AI agent's architecture

Once you know the job, you draw the system before you build it. Most people skip this and build an AI agent from the prompt outward, bolting one piece to the next until it works in the demo, and they end up with a tangle nobody can change. If you cannot draw it, you do not understand it.So you design the AI agent's architecture first: the blocks, the data flow between them, and the modes it can be in.

Why you draw an AI agent before you build it

Skip the drawing and you fall into one of two holes. Built from the prompt out: change one piece and the whole thing shifts, and nobody can say why. It lives in your head: you "know how it works," so you never draw it, and you cannot hand it off, cannot test it, and the one part you cannot draw is the part that breaks. On a satellite nothing is real until it is drawn, reviewed, and signed, because you can never touch it after launch. An agent is the same. The drawing is the understanding.

How an AI agent works: blocks, flows, and states

A system is three things. Blocks, what each part does. Signals, what flows between them. States, the modes the agent can be in. A well-built AI agent runs as a closed loop, the same shape as a satellite's control software: it understands what came in, decides, acts, then checks its own work and corrects, before it repeats. Drawing it as a loop with feedback, rather than a one-way flowchart, is what separates a real agent from a chatbot.

The block diagram: structure and data flow

The first view is the block diagram, what the parts are and what passes between them. Two rules make it flight-grade. Contain the AI to one block so the rest of the flow stays predictable and inspectable, the probability lives in one place, not sprayed across the whole agent. And draw the human hand-off: the path where the agent escalates to a person is on the drawing, on purpose, so a failure is never silent. Every block names an input, an output, and an owner, the agent or a human.

The state machine: the modes and transitions

The second view is the state machine, the same agent seen as the modes it moves through: idle, reading, drafting, checking, sent, with an escalated state for when it is unsure. Name every mode, give every transition a trigger, and always keep a safe state to fall back to (idle), so the agent can always tell whether it is mid-task and never double-replies or drops a thread. This is the AI agent workflow, drawn the way a model-based engineer draws it in a state diagram.

Draw the AI agent in four moves

Drawing a real one is four moves, the order you will use every time. One, list the blocks the job needs. Two, connect them in order and add what they read, the price list and SOPs feed the draft. Three, draw the states it moves through and mark the safe one. Four, mark the single block where the AI lives and draw the escalate path to a human. Four moves and the agent is a system, not a hope.

The Blueprint: the design gate

Those two drawings become your Blueprint, the gate nothing gets built before. It passes when every block has an input, an output, and an owner; the AI is contained to one block; the modes are named with a safe state; the hand-off is explicit; and it fits on one page someone else could build from. Every block on it becomes a requirement in the next step. Once the system is drawn, you write the spec for each block, in numbers, so the agent does the same thing every time.