Zoo vs AdamCAD vs CADGPT: which text-to-CAD tool to use

I spent a Friday afternoon running the same prompt through three different tools. A simple L-bracket, 3mm aluminum, 40mm legs, four M4 clearance holes on a 25mm spacing. Nothing fancy. The kind of part you'd model in Fusion 360 in about eight minutes, which is how I know what the result should look like.

Zoo.dev gave me a STEP file with real B-Rep geometry. AdamCAD gave me an STL with sliders to adjust the dimensions. CADGPT gave me an AutoLISP script. Three different answers to the same question, and none of them wrong exactly, just aimed at different problems. It was like asking three people for directions and getting a map, a bus schedule, and a bicycle.

That experience convinced me these tools aren't really competing with each other, even though they all get lumped under "text-to-CAD." If you're trying to choose between them, the answer depends entirely on what you're trying to do. So let me save you the Friday afternoon.

Zoo.dev: the geometry engine#

Zoo.dev is the one I reach for when I need actual engineering geometry. It runs on a GPU-native kernel called KittyCAD, and the output is real B-Rep: STEP, glTF, OBJ, STL, and several other formats. The free tier is generous enough to actually evaluate the tool, which I appreciate after years of CAD vendors hiding everything behind a sales call.

The workflow is simple. You type a description, wait a few seconds, and get a solid body. The quality depends heavily on how specific your prompt is. "A bracket" gets you whatever the AI's idea of a bracket looks like, which is usually vaguely correct and specifically useless. "A 90-degree L-bracket, 3mm thick, 40mm legs, with two 4.2mm clearance holes per leg spaced 25mm apart, 10mm from the edge" gets you something much closer to what you need. Prompt specificity matters more than anything else with this tool.

What Zoo does well: simple mechanical parts. Brackets, enclosures, mounting plates, standoffs. Geometry that's mostly prismatic with standard features. I've gotten results that needed only minor cleanup in Fusion 360 before they were usable. On a good day, it saves me ten to twenty minutes of sketch-extrude-fillet work.

What Zoo does poorly: anything complex. Gears with functional tooth profiles. Assemblies. Sheet metal with bend allowances. Parts with lots of interdependent features. The accuracy drifts as complexity rises, and by the time you're fixing every dimension manually, you might as well have modeled it from scratch.

The biggest advantage of Zoo is the STEP output. A STEP file opens in SolidWorks, Fusion 360, Creo, NX, or basically any real CAD tool. You get faces, edges, and topology you can actually work with. That makes Zoo a starting-point tool for engineers. Not a finishing tool, but a legitimate starting point. I wrote more about how it performs on specific tasks in the Zoo text-to-CAD review.

AdamCAD: the parametric slider approach#

AdamCAD takes a different angle. You describe a part, the AI generates it, and you get not just an STL file but dimension sliders you can adjust after the fact. Change the height, tweak the hole diameter, adjust the wall thickness. It's parametric in a limited sense, closer to a configurator than a full feature tree, but for simple parts it's surprisingly useful.

The pricing starts at $5.99 a month, which is cheap enough that you don't feel hostile toward the tool before you've even tried it. I tested it with the same bracket prompt, and the output was decent. Not as geometrically precise as Zoo's STEP output, but the ability to drag a slider and change the leg length without re-prompting or reopening my CAD software is genuinely convenient for quick iterations.

Where AdamCAD works: rapid sizing of simple parts. Need a box enclosure and you're not sure if it should be 80mm or 90mm wide? Generate it once, drag the slider, see both options. For hobbyists, for early prototyping, for "I just need a bracket and I don't want to learn SolidWorks," this is probably the most approachable of the three tools.

Where it falls short: the parametric controls are limited. You get sliders for the dimensions the AI decided to expose, which may or may not be the ones you care about. You can't add new features, create relationships between dimensions, or do anything that requires actual constraint logic. And the STL-only output means you're stuck with mesh geometry, which is fine for 3D printing and useless for engineering edits. If you need to select a face, add a fillet, or export a proper drawing, you're out of luck.

The AdamCAD review goes into more detail on specific use cases and where the parametric controls actually help versus where they're just decoration.

CADGPT: the script writer#

CADGPT is the odd one out, and I think the name causes most of the confusion. It doesn't generate CAD geometry at all. It writes automation scripts. AutoLISP for AutoCAD, Python for other environments. If you tell it to make a bracket, you don't get a bracket. You get code that, if executed in the right environment, should produce a bracket.

This is a fundamentally different proposition. CADGPT is a coding assistant for CAD automation, not a geometry generator. It's closer to GitHub Copilot for AutoLISP than it is to Zoo or AdamCAD.

For the right user, that's actually valuable. If you spend your days writing AutoLISP routines to batch-process drawings, or you need Python scripts to automate FreeCAD operations, or you want to generate OpenSCAD code without typing it character by character, CADGPT can speed that up. I tested it with a request to write an AutoLISP script that draws a configurable bolt pattern on a rectangular plate. The script was functional, needed some tweaks to the error handling, and saved me about twenty minutes of writing it myself.

But if you're expecting to describe a part and receive a model, CADGPT will disappoint you. You receive text, not geometry. You need a CAD environment to execute that text, and you need enough knowledge to debug the script when it doesn't quite work. That's a different skill set from "describe a part and get a part."

The CADGPT review covers the scripting capabilities more thoroughly, but the short version is: useful tool, wrong category. It shouldn't be compared with Zoo and AdamCAD because it's solving a different problem.

The comparison that matters#

Here's the clearest way I can break it down.

If you need engineering geometry you can import, edit, and manufacture: Zoo.dev. The STEP output, the B-Rep quality, and the API access make it the most serious tool for engineers. The output still needs checking and editing, but it's real geometry, not a mesh or a script.

If you need quick simple parts with adjustable dimensions and you're heading straight to 3D printing: AdamCAD. The slider approach is smart for the kind of user who doesn't want or need a full CAD environment. Just don't expect engineering-grade output.

If you need help writing CAD automation scripts: CADGPT. It's a coding tool that happens to know CAD-specific languages. Nothing wrong with that, as long as you know what you're getting.

If you need complex parts, assemblies, tolerances, sheet metal, or anything that requires actual engineering judgment: none of the above. You need traditional CAD software and, ideally, someone who knows how to use it. I'm not being dismissive. The text-to-CAD guide covers how these tools fit into professional workflows, and the honest answer is: they fit at the beginning, not the end.

Where the confusion comes from#

The problem is that all three tools get called "text-to-CAD" even though they do different things. Zoo generates geometry. AdamCAD generates configurable shapes. CADGPT generates code. Calling all of these text-to-CAD is like calling a hammer, a screwdriver, and a tape measure "construction tools." Technically true, practically misleading if you need to drive a nail.

The best text-to-CAD tools comparison covers the full field, including tools like CADAgent and CADScribe that take yet other approaches. The space is early and fragmented, which is normal for new technology. But the fragmentation means you need to know what each tool actually does before you pick one, because picking the wrong tool won't just give you a bad result. It'll give you a result in the wrong format for the wrong problem, and you'll blame "text-to-CAD" when you should blame the choice.

My honest take#

I use Zoo.dev for quick starting geometry when I'm doing simple parts and I want a faster first draft than sketching from scratch. I've looked at AdamCAD for cases where I need to explore dimension ranges quickly without opening Fusion 360. I haven't integrated CADGPT into my workflow because I don't write enough AutoLISP to justify it, but I can see the appeal for someone who does.

None of these tools replaces the other two. None of them replaces traditional CAD. And none of them is as good as the marketing copy suggests. But each one does a specific thing reasonably well, and knowing which thing that is saves you from the frustration of expecting a STEP file and getting a script, or expecting parametric control and getting a dumb solid.

Pick the tool that matches the problem. It sounds obvious, but in a market where every tool is trying to be the everything-tool, obvious advice is the kind that gets ignored the most.