How to generate CAD from text: the honest version

Last Tuesday I was trying to show a colleague how text-to-CAD works. I typed a perfectly reasonable prompt into Zoo.dev, something like "rectangular enclosure, 100mm by 60mm by 40mm, 2mm wall thickness, four M3 mounting holes in the corners." The model came back in about fifteen seconds. My colleague looked impressed. Then I opened the STEP file in Fusion 360, measured the wall thickness, and it was 3mm. Not 2mm. I fixed it in about a minute, but the look on his face had already shifted from "wow" to "ah." That shift is the honest version of text-to-CAD in one facial expression.

You can absolutely generate CAD geometry from a text description. The tools exist, they work, and for simple parts they save real time. The honest part is that "generate" is the easy half of the sentence. The other half is "verify, fix, and finish," and that half takes longer than anyone's demo suggests.

The actual process#

The basic flow is the same regardless of which tool you use:

1. Write a text description of the part you want, with specific dimensions.
2. Feed it to a text-to-CAD tool.
3. Wait ten to thirty seconds.
4. Inspect the result.
5. Export as STEP.
6. Import into your real CAD software.
7. Measure everything that matters.
8. Fix what's wrong.
9. Add what's missing.

Steps 7 through 9 are where the actual work lives. Steps 1 through 6 are the part that looks good in a demo.

Choosing a tool#

Right now, in early 2026, your practical options are:

Zoo.dev is the most developed dedicated text-to-CAD platform. It runs on a custom GPU-native geometric kernel, outputs real B-Rep geometry as STEP files, and has a free tier generous enough to test properly. For a full walkthrough, I wrote a how to use text-to-CAD guide, and the text-to-CAD guide covers the broader landscape.

CADAgent is an open-source Fusion 360 add-in that generates models inside Fusion itself, which means the output has actual feature history. You bring your own Anthropic API key. It's the most promising approach for integration with a real CAD workflow, because the geometry is created using Fusion's own modeling commands rather than generated externally and imported.

AdamCAD generates parametric models with adjustable dimension sliders. Faster for quick prototyping, but the parametric controls are limited compared to a native feature tree.

CADScribe outputs STEP and STL files and has gotten some traction with the 3D printing crowd. Mixed results on anything beyond simple geometry.

The best text-to-CAD tools comparison covers all of these with more detail on pricing, capabilities, and limitations.

For this walkthrough, I'll use Zoo.dev because it's the most accessible starting point and produces the cleanest STEP output.

Writing a prompt that works#

This is the part that separates a useful generation from a waste of time. The AI responds to specificity. Vague descriptions produce vague parts. Precise descriptions with explicit dimensions produce parts that at least attempt to be what you asked for.

Bad prompt: "make a bracket for a sensor."

Better prompt: "L-bracket, 3mm thick, 45mm tall leg, 35mm base leg. Two M4 clearance holes on the base, spaced 25mm apart, centered on the base width. One M4 clearance hole on the tall leg, centered at 30mm height."

The difference in output quality between those two prompts is enormous. The first one gives you whatever the AI thinks a sensor bracket looks like. The second one gives you something with actual engineering intent behind it.

Rules I've learned after months of this:

Always include units. Always. If you say "50" the AI might interpret that as millimeters, inches, or something in between. Say "50mm."

Name standard features explicitly. "M4 clearance hole" works better than "4mm hole" because the AI maps it to the correct clearance diameter. "Mounting boss" works better than "raised section with a hole."

Describe positions in absolute terms. "15mm from the left edge" beats "near the left edge." "Centered on the 40mm dimension" beats "roughly in the middle."

One part per prompt. Don't try to generate an assembly. Generate each piece separately with compatible dimensions.

The text-to-CAD tutorial goes into more detail on prompt structure, and the prompt engineering post explores the nuances of phrasing that consistently produces better geometry.

What happens after generation#

You've typed your prompt, waited the fifteen seconds, and the viewport shows something that looks roughly like your part. Now the work begins.

Export as STEP. Not STL, not OBJ, not glTF. STEP. This is the format that gives you real solid geometry with selectable faces and measurable edges. Everything else is either a mesh (useful for 3D printing, useless for engineering edits) or a visualization format (useful for nothing you care about right now).

Open the STEP file in Fusion 360, SolidWorks, or whatever you actually model in. The file should import as a solid body. If your CAD software shows a mesh import warning instead of a solid body, something went wrong with the export format.

Now measure. Every dimension you specified in the prompt, check it. I keep a simple mental checklist:

Is the overall size correct? Length, width, height. Check all three.

Are the holes the right diameter? Select the hole edges and verify. M4 clearance should be about 4.3mm to 4.5mm. If it's 4.0mm, that's not clearance, that's a press fit nobody asked for.

Are the features in the right positions? Measure from edges to hole centers. Check spacing between holes. Verify symmetry if you asked for it.

Is it actually a solid? Sometimes the geometry looks closed but has an invisible gap or an internal face that makes it technically a surface body rather than a solid. Check your CAD software's body type indicator.

On a typical simple part, I find one or two things that need fixing. A dimension off by a millimeter. A hole that shifted slightly. A missing fillet or chamfer I forgot to include in the prompt. On a more complex part, the fix list grows to the point where I'm essentially rebuilding it, at which point I would have been faster starting from scratch.

The cleanup reality#

Here's the thing nobody puts in the demo: cleanup is where text-to-CAD time actually goes. The generation takes fifteen seconds. The export and import take another thirty seconds. The measuring and fixing take five to twenty minutes, depending on complexity and accuracy.

For a simple mounting plate with holes on a bolt pattern, cleanup might be just checking dimensions and adding corner radii I forgot to specify. Total saved time versus modeling from scratch: maybe five minutes. Worth it.

For a moderately complex part, say an enclosure with bosses, a lip, screw posts, and vent slots, the generated geometry usually gets the overall shape right but misses the details. The bosses aren't the right height. The lip doesn't have the right clearance for a mating lid. The vent slots are decorative rather than dimensioned. By the time I've fixed all of that, I've spent more time than modeling from scratch would have taken, plus I'm working with imported geometry that doesn't have a clean feature tree.

This is not a condemnation of the technology. It's a calibration of expectations. For the right kind of part, text-to-CAD is genuinely faster. For the wrong kind, it's a scenic detour. Learning to tell the difference is the skill that matters.

What kinds of parts actually work#

Simple prismatic geometry. If the part is fundamentally a combination of rectangular extrusions, cylindrical holes, fillets, and chamfers, text-to-CAD handles it. Brackets, plates, standoffs, basic housings, spacers, adapter plates with bolt patterns. These are the bread-and-butter parts that make up a surprising amount of mechanical design work, and they're exactly where the tools deliver.

What doesn't work: anything where features have complex relationships. Gears with involute profiles. Sheet metal with bend allowances. Snap-fit features with undercuts. Draft angles for injection molding. Lofted surfaces. Swept profiles. Multi-body assemblies. The tools will attempt some of these and produce geometry that looks plausible at a glance but falls apart the moment you try to manufacture or assemble it.

If you're not sure whether your part is in the "works" category, ask yourself: could I describe every feature with a dimension and a position, without needing to reference curves, surfaces, or relationships between moving parts? If yes, try it. If no, model it by hand.

The bigger picture#

Text-to-CAD is not a replacement for knowing how to use CAD software. It's a first-draft generator. The useful analogy is autocomplete: it gets you started faster, but you still need to know what a correct sentence looks like.

Where it fits in my workflow: I use it for simple parts that I'd otherwise spend ten minutes sketching and extruding. Sensor brackets, test fixture plates, cable routing clips, mounting adapters. Parts where the geometry is trivial but still takes time to draw from nothing. On those parts, text-to-CAD saves me a few minutes each, which adds up across a week of prototyping work.

Where it doesn't fit: anything going to a machine shop, anything with tolerances that matter, anything that mates with another part in an assembly with clearance fits. For those, I model from scratch in Fusion 360, because I need control over the feature tree, proper constraints, and the ability to update dimensions without reimporting a new STEP file.

The honest version of how to generate CAD from text is: you generate it, you verify it, and you fix it. The generation is fast and occasionally impressive. The verification and fixing are the work. Budget your time accordingly, and the tool is genuinely useful. Expect it to produce finished parts, and you'll spend your afternoon arguing with imported geometry instead of designing.