# How the assistant works

The assistant changes your design with the same validated commands that you use, it makes no compliance claims, and each request costs credit.

The assistant is an AI model that operates KerfCraft for you. You tell it what to build or change, and it uses the app's commands to do it.
This page explains how it works, what it can and cannot do, and why it costs money. To use it, read [Use the assistant](/docs/how-to/assistant/use-the-assistant/).

## The assistant uses your commands

The assistant has no separate copy of your design. It uses the same commands that the toolbar and **Properties** use, with the same checks.
If a command is not correct, KerfCraft refuses it, and the assistant reads the reason and tries again.
Each change goes on the undo list, as your own changes do. Thus **Undo last request** can remove everything that the assistant did for one message.

The assistant reads the design with commands too, for example to list the components or to examine one part. It can also look at an image of the 3D view.
When it names a component in a reply, you can click the name to select that component.

Read [How KerfCraft works](/docs/explanation/how-kerfcraft-works/) for more about the commands.

## What the assistant knows about your request

Each message goes with the components that you selected or named with **@**. The assistant uses them to know which parts you mean.
If you select **Only change these**, KerfCraft refuses each change outside those components. The assistant can still read the whole design.

## Checks after a request

When the assistant stops, KerfCraft runs its design checks again. It looks only for problems that the request added.
If a change breaks a check, KerfCraft tells the assistant to correct it, or to tell you that the result is intended.
If the problem stays, the panel shows a warning with the checks that still fail.

The assistant can do many steps for one message. After many steps, it pauses so that you can examine the work. You click **Continue** to let it work on.

## What the assistant does not promise

The assistant is told never to claim that a structure is strong enough. It is told never to claim that a design obeys Building Regulations or planning rules.
Its checks on room sizes, headroom and stairs are advice only. It does not replace an architect or a structural engineer.

An AI model can make mistakes. Examine what the assistant made before you use it.
The manufacturing promise is the same for a part that the assistant made and a part that you drew. Read [What KerfCraft checks and what you must check](/docs/explanation/what-kerfcraft-checks/).

## Why each request costs money

KerfCraft pays the AI provider for each request, and you pay with AI credit. The price depends on the model and on the number of tokens.
The model reads the whole conversation and the parts of the design that it asks for, and it writes its reply and its commands.

Each request sends the whole conversation again. Thus the later messages in a long conversation cost more than the first messages.
A part of the conversation that the model read recently can come from a cache, at a lower price.
When a conversation gets long, the panel suggests a new chat. A new chat is cheaper, and your design does not change.

A higher effort lets the model think more, so it costs more. The panel shows the price of the selected model before you send a request.
Read [Check what AI help costs and top up credit](/docs/how-to/assistant/top-up-ai-credit/).

## Where your messages go

Your messages, the parts of the design that the model needs, and your images go through KerfCraft's server to Vercel's AI Gateway. The Gateway sends them to the provider of the model that you selected.
Read [Where your designs are stored](/docs/explanation/where-your-designs-are-stored/).