Zoo text-to-CAD tutorial: step by step

I spent my first half hour with Zoo.dev typing prompts that sounded perfectly reasonable to me and getting back geometry that looked like it had been designed by someone who'd had the part described to them over a bad phone connection. The proportions were close. The intent was there. The details were wrong in small, expensive ways. A hole pattern shifted 5mm from where I asked for it. A wall thickness that quietly doubled itself. A fillet radius that the tool apparently decided was a suggestion rather than an instruction.

The second half hour went better, because I'd figured out what the tool actually listens to and what it ignores. This tutorial is the version I wish I'd had before that first session.

Setting up an account#

Go to zoo.dev and create a free account. Email and password, or sign in with GitHub. The free tier gives you enough API calls per month to properly test things. You don't need a credit card to start.

Once you're logged in, you'll land on the Design Studio. It's sparse on purpose: a text box, a 3D viewport, and a few export buttons. There's no feature tree, no sketch panel, no timeline. If you're used to the density of Fusion 360 or SolidWorks, the emptiness might feel suspicious. Don't worry. The simplicity is the point. Zoo generates geometry from text. What you do with that geometry afterward happens in your real CAD tool.

If you plan to use the Python API later, you can generate an API key from your account settings. For this tutorial, we'll stick to the web interface.

Your first prompt#

Here's where most people trip up, myself included. The natural instinct is to type something conversational: "make me a bracket for mounting a small PCB." That will produce a bracket. It will also produce a bracket with dimensions the AI invented, hole sizes that may or may not correspond to any actual fastener, and proportions that came from whatever the model's internal average bracket looks like.

Instead, be specific. Treat the prompt like you're filling out a drawing title block, not describing the part to a friend over lunch.

Try this: "L-bracket, 3mm thick, 50mm tall leg, 40mm base leg, two M4 clearance holes on the base spaced 25mm apart and centered, one M4 clearance hole centered on the tall leg at 35mm height."

Type that into the Design Studio text box and click Generate. You'll wait somewhere between ten and thirty seconds. The 3D viewport will populate with a model.

Rotate it. Look at it from a few angles. Does it look like what you described? In my experience, a prompt like that one returns something recognizably correct about 80% of the time. The other 20%, you get a bracket where one of the holes decided to migrate, or the thickness came back at 4mm instead of 3mm, or the base leg is 45mm because the AI felt generous.

This is normal. Welcome to text-to-CAD.

Inspecting the output#

The Design Studio viewport lets you rotate, zoom, and pan. It doesn't let you measure. That's the first limitation you'll feel. You can see the geometry, but you can't confirm the dimensions without exporting and opening the file in a real CAD tool.

Look for obvious problems first. Is the shape roughly right? Are the holes visible? Does the part have the right number of features? If the AI generated something wildly different from your prompt, don't bother exporting. Just rephrase and regenerate.

If the shape looks correct at a glance, move to the export step. The real inspection happens in Fusion 360 or SolidWorks, where you can actually select faces, measure distances, and check diameters.

Exporting as STEP#

Click the export button and choose STEP. Zoo also offers glTF, OBJ, STL, and a few others, but STEP is the one you want for engineering work. STEP gives you real B-Rep geometry with selectable faces and measurable edges. STL gives you a triangle mesh that your CAD software will treat like a foreign object.

The STEP file downloads to your machine. It's typically small, a few hundred kilobytes for simple parts. If you've been dealing with mesh files from other AI tools, the file size alone tells you something: this is compact mathematical surface data, not a million triangles pretending to be a cylinder.

For a deeper look at why the file format matters so much, I covered that in text-to-CAD to STEP file: getting usable output.

Importing into Fusion 360 (or SolidWorks)#

Open Fusion 360. File, Open, select the STEP file. It'll import as a solid body. You should see real faces in the browser panel, not a mesh import warning.

Now measure things. Select two parallel faces and check the thickness. Select a hole edge and check the diameter. Measure the distance between hole centers. Compare everything to what you asked for in the prompt.

On a good day, the dimensions will be within a fraction of a millimeter. On a bad day, you'll find the kind of discrepancies I mentioned earlier: 5% off on a critical dimension, a hole that shifted, a feature that's geometrically present but not where you specified it. I always measure. Always. Not because I don't trust the tool, but because I've been burned enough times by tools I did trust to know better.

If the geometry is close but not perfect, you can fix it right there in Fusion. Move a hole with a sketch edit. Adjust a dimension. Add a fillet the AI forgot. This is faster than re-prompting and hoping the next generation gets it right.

For a broader view of how text-to-CAD fits into an actual workflow, the text-to-CAD guide covers the whole picture.

Writing better prompts#

After a few dozen generations, I've settled on some patterns that consistently produce better results.

Always include units. "50mm" is better than "50." Without units, the AI guesses, and its guesses aren't always in the unit system you're thinking in.

Specify thickness, height, and width explicitly. Don't assume the AI will infer "structural" thickness for a bracket or "reasonable" wall thickness for an enclosure. It won't. Or rather, it will, and its idea of reasonable will not match yours.

Name standard features. "M4 clearance hole" is better than "4mm hole" because the AI seems to understand that M4 clearance means 4.3mm or 4.5mm diameter, depending on which standard it's pulling from. "Four M3 mounting bosses in the corners" works better than "holes in the corners."

Describe positions relative to edges or other features. "Two holes 15mm from the left edge, spaced 30mm apart" gives the AI anchors. "Two holes on the left side" gives it creative freedom, which is not what you want from a dimensioned part.

Keep it to one part per prompt. Assemblies are beyond what Zoo handles. If you need two mating parts, generate them separately with compatible dimensions.

The text-to-CAD prompt engineering post goes much deeper into strategies that work and phrasings that don't.

When it works and when it doesn't#

Zoo handles prismatic parts well. Anything you could describe as a combination of extrusions, cuts, holes, fillets, and chamfers on a rectangular or cylindrical base has a good shot. Brackets, plates, enclosures, standoffs, adapter plates, spacers. The geometry comes back as proper solids, and the STEP files open cleanly everywhere I've tested.

It does not handle complex curvature, organic shapes, lofted surfaces, or swept features. Don't ask it for an aerodynamic housing with compound curves. Don't ask it for a gear with involute tooth profiles. Don't ask it for a snap-fit enclosure with proper draft angles. I've tried all of these. The results range from "that's not quite right" to "that's not even the right category of wrong."

Sheet metal is another gap. Zoo doesn't know about bend allowances, K-factors, or flat patterns. It'll give you something that looks like folded metal but was never modeled with bending in mind. If your part needs to unfold, you're not starting here.

Multi-body assemblies don't exist in Zoo's generation. One prompt, one solid body. That's it.

For an honest assessment of where Zoo sits in the broader tool landscape, the Zoo text-to-CAD review covers capabilities, pricing, and limitations without the marketing gloss.

A real example, start to finish#

I'll walk through an actual part I generated last week. I needed a sensor mounting plate for a test fixture: rectangular, 80mm by 50mm, 4mm thick, with four M3 clearance holes on a 70mm by 40mm bolt pattern, and a central 12mm through-hole for a cable grommet.

My prompt: "Rectangular plate, 80mm by 50mm, 4mm thick. Four M3 clearance holes on a 70mm by 40mm rectangular bolt pattern centered on the plate. One 12mm through-hole at the center of the plate."

Generation took about fifteen seconds. The result in the viewport looked right. Four small holes near the corners, one larger hole in the middle, flat rectangular shape.

I exported as STEP, opened in Fusion, and measured. The plate was 80.0mm by 50.0mm by 4.0mm. The bolt pattern was 70.0mm by 40.0mm. The M3 holes were 3.4mm diameter, which is correct for M3 clearance fit. The center hole was 12.0mm. Everything was where I asked for it.

This is Zoo at its best: a simple, well-described prismatic part with explicit dimensions, generating clean geometry in under twenty seconds. I added corner radii in Fusion because I didn't ask for them in the prompt, applied a chamfer to the top edges, and sent the STEP to a colleague. Total time from prompt to finished part: about four minutes. Modeling it from scratch in Fusion would have taken maybe eight. Not a massive savings, but real.

The trick is that not every prompt goes this smoothly. The part before this one, a U-shaped channel with unequal legs and a slot in one side, came back with the slot on the wrong leg and the overall width off by 6mm. I re-prompted twice before giving up and just modeling it in Fusion. Sometimes the tool saves time. Sometimes it costs time. Knowing which kind of part falls into which category is the skill you develop after a few weeks of using it.

What to do next#

If you've gotten through your first generation and export, you have a feel for what Zoo does and doesn't do. The next steps that helped me the most were learning to write tighter prompts and understanding which kinds of geometry are worth generating versus modeling by hand.

The text-to-CAD guide covers the full landscape of tools and approaches. If you want to go beyond the web interface, the Zoo text-to-CAD API tutorial walks through scripting batch generations with the Python SDK, which is where Zoo starts to feel genuinely powerful.

Zoo is not a replacement for CAD skills. It's a shortcut for the boring parts, when the shortcut works. After a month of using it, I generate simple parts there and model anything with real complexity in Fusion. That split saves me maybe an hour a week, spread across a dozen small parts that I'd otherwise have to sketch from scratch. Not transformative. But an hour a week, every week, adds up to enough that I keep the browser tab open.