AI CAD comparisonAdam vs FeatureScript MCP: skip the code, keep the CAD.
PTC's FeatureScript MCP server hands an AI a code editor and a documentation search tool, then leaves you to review the FeatureScript it writes. Adam is a dedicated mechanical-engineering agent. It does the FeatureScript work invisibly, runs on purpose-built CAD skill modules, and lets you pick the model behind it. No code to read, no allocation to run out of.
New to the FeatureScript MCP server? Read the explainer first.
At a glance
Code you review, or CAD that's done.
FeatureScript MCP hands your AI a code editor. Adam hands you back the finished part.
FeatureScript MCP
An early-access PTC server that lets a general-purpose AI client write and test FeatureScript, Onshape's parametric programming language, inside a Feature Studio. There's no dedicated engineering agent here. It's a chat model pointed at a documentation search tool, and the output is code you still have to read, debug, and trust, metered against an Onshape API allocation that runs out.
Adam
A dedicated mechanical-engineering agent with purpose-built skill modules for CAD. Adam already runs FeatureScript under the hood, invisibly, and hands back the finished CAD change, not code for you to review. Pick the model powering your work: Anthropic, OpenAI, Google, or xAI. Never touch a Feature Studio unless you want to. Tighter integration, better tools, one product.
Side by side
Adam vs FeatureScript MCP, feature by feature.
| Dimension | FeatureScript MCP | AdamRecommended |
|---|---|---|
| What it is | An Onshape Labs MCP server where a general-purpose AI client writes, tests, and iterates FeatureScript custom features. | A dedicated mechanical-engineering agent that edits parts and assemblies in Onshape directly from prompts, plus a text-to-CAD workspace. |
| Model choice | Bring your own AI client and pay for it separately, on top of your Onshape plan and its API allocation. | Pick the model powering your work: Anthropic, OpenAI, Google, xAI, and more, included in your plan. |
| Engineering expertise | A general-purpose chat model writing code against a documentation search tool, with no mechanical-engineering training. | Runs on dedicated mechanical-engineering skill modules for CAD: purpose-built tools, not a chat model guessing at code. |
| The output | FeatureScript code, a reusable custom feature you still have to review, debug, and trust. | Finished CAD work: model edits, new parametric parts, cleaner feature trees, and reconciled BOMs. No code to read. |
| Who it's for | FeatureScript authors comfortable reading and debugging C-family code. | Any engineer or hardware team; no programming required. |
| Setup | Subscribe via the Onshape App Store, opt into Onshape Labs, and configure a separate AI client. | Install the Adam extension from the Onshape App Store and start prompting. |
| Usage limits | Every tool call consumes a metered Onshape API allocation. Requests fail once it's gone. | Usage is included in your Adam plan, nothing to run out of. |
| When the AI writes code | You read the code. Documentation search and live testing reduce hallucinated functions, but debugging is still on you. | Adam runs FeatureScript and the Onshape API under the hood, invisibly, with documentation lookup and regeneration checks handled for you. |
| Platform reach | Onshape only. | Every model Adam produces stays parametric and editable, across the CAD platforms Adam supports, with more added over time. |
The verdict
Why teams outgrow FeatureScript MCP.
FeatureScript MCP earns real credit in one narrow lane: authoring reusable custom features. Outside that lane, Adam is simply the better tool.
What FeatureScript MCP offers
- If you specifically want to author a reusable custom Onshape feature and are comfortable reading code, PTC's tooling is a legitimate, well-built option.
- It's free to experiment with on Onshape's public-document tier, if you don't mind everything you build being public.
Why Adam wins
- No code to write, read, or debug. Adam does the FeatureScript work and hands back the finished part.
- Not locked into one AI vendor. Pick the model that powers your work: Anthropic, OpenAI, Google, or xAI.
- A dedicated mechanical-engineering agent with CAD-specific skill modules, not a chat model pointed at a docs search tool.
- No metered API allocation to run out of. Usage is included in your plan.
- Works across CAD platforms, not one, with more added over time.
- Handles the BOM and sourcing work around the model too.
Deep dive
What is FeatureScript?
FeatureScript is the programming language Onshape built for parametric 3D modeling. You write it in a Feature Studio, a code-editor tab inside an Onshape document, declaring parameters in a precondition block and geometry operations in a body. It's a real C-family language with a real learning curve, historically the domain of Onshape power users comfortable reading code.
Deep dive
What is the FeatureScript MCP server?
The Onshape FeatureScript MCP Server is PTC's early-access Onshape Labs release: a hosted server that connects a general-purpose AI client to Onshape so it can write, test, and iterate FeatureScript. Notice what that is. Not a mechanical-engineering agent, but a chat model pointed at a code editor and a documentation search tool, trying to avoid hallucinating standard-library functions long enough to produce working code.
The output is a custom feature, code, not a finished part, and the debugging loop still happens at the level of reading FeatureScript and regeneration errors. Every tool call also draws from a metered Onshape API allocation. An agentic write-test-fix loop burns through that fast, and once it's gone, requests fail until you buy more.
Deep dive
What is Adam?
Adam is a dedicated mechanical-engineering agent, working across CAD platforms, including Onshape and Autodesk Fusion today, with more on the way. Instead of routing a general chat model at raw FeatureScript, Adam runs on purpose-built skill modules: dedicated tooling for feature trees, parametrization, sketch constraints, and BOM logic, engineered specifically for CAD rather than improvised against documentation.
Adam already writes FeatureScript where it's the right tool, with documentation lookup and regeneration checks built in. That's the same discipline PTC's server encourages, handled for you, invisibly. The deliverable is the finished model: a branched edit, a new parametric part, a reconciled BOM, not a Feature Studio tab for you to debug. And Adam isn't locked to one AI vendor. Pick the model that powers your work, Anthropic, OpenAI, Google, or xAI, instead of managing a separate AI subscription on top of your Onshape plan.
Deep dive
How to choose
There's exactly one job the FeatureScript MCP server is genuinely built for: authoring a reusable custom feature that your whole team adds to the Onshape toolbar, if you're comfortable reading and debugging code. That's a real, narrow use case, and PTC's tooling handles it seriously.
For everything else, modeling a part, editing an existing one, cleaning up a feature tree, or reconciling a BOM without touching a line of code, Adam is the engineering agent built to do the job outright. It runs FeatureScript for you when that's the right tool, lets you pick the model behind it, and never asks you to open a Feature Studio.
Put Adam to work in Onshape.
Edit Onshape parts from prompts, generate parametric models from scratch, pick the AI model that powers your work, and let a dedicated mechanical-engineering agent handle the FeatureScript layer, plus the BOMs and sourcing around it.