# Natural language CAD: how a prompt becomes a feature operation > What separates an instruction that resolves into a real SOLIDWORKS feature from one that does not. Plus the prompt patterns that actually work. URL: https://cadabrai.com/natural-language-cad/ Updated: 2026-08-15 --- # Natural language CAD. How to write an instruction that resolves into a real feature, and what makes one fail. ## What natural language CAD means. Natural language CAD is issuing modelling instructions in ordinary engineering language and having a system execute them as real CAD operations. It is distinct from **generative design**, which produces shapes algorithmically from loads and constraints, and from **text to mesh**, which produces triangles that were never parametric. After the system acts, is there a feature in the tree you could have created yourself? If yes, it is natural language CAD. If not, it is generation of something else. ## undefined 1. 01 Parse the intent "Fillet all sharp edges on this face at 2 mm" is one operation, one reference, one dimension, and one implicit selection rule. 2. 02 Resolve against the open model Turn "this face", "that hole pattern", and "the boss I just made" into specific entities in the live document. This is the step a tool outside your CAD seat cannot perform, because it has no document to resolve against. 3. 03 Choose the operation and its parameters Apply the standards you configured rather than defaults. 4. 04 Execute, rebuild, and verify You are told whether the rebuild succeeded and exactly what changed. ## Vague prompt, specific prompt. Every instruction needs an operation, a reference, and a number. Drop any one of the three and it cannot resolve. **Make it stronger** Fails. No operation, no reference, no number. **Add a 3 mm rib from the boss to the outer wall, patterned 8 times about the axis** Resolves. One operation, two references, two numbers, one pattern rule. **Clean up the corners** Fails. "Corners" is not a selectable set and "clean up" is not an operation. **Fillet every edge under 2 mm radius on the top face at 1 mm** Resolves. The selection rule is explicit and the face is referenced. **Make the holes bigger** Ambiguous. Which holes, and by how much, and does the counterbore follow? **Change the four Ø6 through holes on the flange to Ø8, keep the counterbores concentric** Resolves. Count, current size, feature, new size, and the downstream rule are all stated. ## Why resolution is the hard part. The difficulty in CAD is not understanding the sentence, it is that the sentence refers to a specific document: a face somebody selected, a feature created three operations ago, a configuration that only exists in one file. That is why a browser tool that takes a prompt and returns a file cannot do this work at all. It has no open document, no selection, and no history. CADABRA runs inside SOLIDWORKS for that reason. ## Natural language CAD, answered. ### How does a natural-language prompt become geometry? You write the change in plain English, naming the face or feature and the dimension. CADABRA resolves that against your open model and makes the edit; the model is rebuilt, and the result is checked. ### Is natural-language CAD the same as generative design? No. Generative design produces shapes algorithmically from loads and constraints, usually organic and topology-optimised. Natural-language CAD performs the operations an engineer describes, in the order they describe them, on the model they already have. ### What kind of prompts actually work? Concrete, dimensioned, engineering-language prompts work best. Examples: “make the wall 3 mm thicker”, “fillet all sharp edges on this face at 2 mm”, “add a 6 mm counterbored hole pattern on a 40 mm bolt circle”, “pattern this rib eight times around the axis”, “change the material to 6061-T6 and update the mass properties”. Vague prompts such as “make it better” do not resolve to a single operation. ### How accurate is it, and who checks the work? You do. CADABRA performs real operations on your model and shows exactly what it changed, so every edit is reviewable in the feature tree and revertible. ### Why not just write a macro or an API script? Macros work for a fixed, repeated sequence: they break when the feature tree changes, they need a developer to maintain, and each new variation is a new script. CADABRA resolves intent against the actual model at run time, so one prompt covers cases that would otherwise need a separate macro each. ### Do I need my own SOLIDWORKS license? Yes. CADABRA is an add-in, not a CAD system. You keep your existing SOLIDWORKS license, files, libraries, and PDM, and CADABRA works inside them. ## Write one and watch it resolve. Bring a part to a 20-minute call, or install it and try your own prompt. ## Keep reading - [Text to CADPrompts that resolve into native SOLIDWORKS features, not an imported mesh.](https://cadabrai.com/text-to-cad/) - [ChatGPT for CADWhat a general chatbot can do with your model, and what it cannot.](https://cadabrai.com/chatgpt-for-cad/) - [AI CADWhat AI CAD does today, and what it does not.](https://cadabrai.com/ai-cad/) - [GlossaryAI CAD and mechanical design terms, one paragraph each.](https://cadabrai.com/glossary/)