Documentation
Using AI with ProtoJoint
There are two ways. Eleph, the built-in AI design assistant, models in the open design when you ask it to. An MCP connection lets an AI app you already use, such as Claude Desktop, claude.ai, Claude Code, Cursor or ChatGPT, work on the design open in your browser tab. Both need a ProtoJoint account with a confirmed email address; accounts are by invitation during the beta. Every paid plan has Eleph; MCP connections come with Max, and Maker and Pro have 100 calls a month to try them. Modeling without AI stays free and needs no account.
What can the AI do in a design?
It uses the same tools you do, through a fixed set of actions:
- read the design (its components, bodies, features and parameters) and any sketch in it;
- start a new design, start a sketch on the XY, XZ or YZ plane, draw in it, and add constraints and named dimensions;
- change a dimension or a parameter by name;
- extrude, revolve, fillet, chamfer and shell, and delete a feature;
- undo and redo;
- look at the model in a screenshot, and measure a body’s volume, mass, centre of mass and bounding box;
- save the design to your computer as STEP, STL or a ProtoJoint file.
Everything it builds is ordinary features on the timeline: you can edit, undo or delete them like your own.
How do I use Eleph?
Sign in, confirm your email address, click Eleph in the header, and describe what you want: “a 40 × 20 mm plate, 10 thick, with R3 corners and a 6 mm hole in the middle”. Eleph sketches, dimensions and builds it in the open design, where you can check and change every step. It runs on Claude Sonnet 5.5 with the Maker and Pro plans, and on Sonnet 5.5 or Opus 5.5 with Max. A free account that contributes its designs and AI sessions to improve ProtoJoint's AI gets 50 credits a month for it. Before a message goes, the chat shows an estimate of the credits it will use.
How do I show Eleph a picture or my own marks?
Paste a screenshot into the chat, drop picture files on the chat or the view, use the picture button under the chat’s input, or, on a phone or tablet, the camera button. A message can carry up to five pictures in PNG, JPEG, WebP or GIF; other formats the browser can read are converted first.
To point at something in the model, click Markup at the bottom left of the view and draw over it with the Pen, Arrow, Line, Dimension, Ellipse, Box, Text and Eraser tools. Send to Eleph attaches the view with your marks to the chat; Save image downloads it as a PNG and needs no account. The screenshots Eleph takes for itself appear in the chat under the step that took them, so you can see what it saw.
How do I connect Claude Desktop or claude.ai?
- In ProtoJoint, open your account menu and choose AI connections.
- Turn on Let AI apps control this tab, and copy the MCP server URL:
https://protojoint.ai/mcp. - In Claude, go to Settings, Connectors, Add custom connector, paste the URL, and sign in to ProtoJoint when asked.
Keep the ProtoJoint tab open while the AI works; it can be in the background. The AI acts on the design open in that tab.
How do I connect Claude Code?
Create an API key under AI connections (it is shown once, so copy it), then run:
claude mcp add --transport http protojoint https://protojoint.ai/mcp --header "Authorization: Bearer <API key>"How do I connect Cursor or another MCP client?
Add the server to the client’s mcp.json with an API key:
{
"mcpServers": {
"protojoint": {
"url": "https://protojoint.ai/mcp",
"headers": { "Authorization": "Bearer <API key>" }
}
}
}Any client that speaks MCP over HTTP can connect the same way. ChatGPT, and other apps that add a remote MCP server by its URL, sign in to ProtoJoint when asked, as Claude does.
What does it cost?
Every paid plan has Eleph: Maker and Pro with Claude Sonnet 5.5, Max with Sonnet or Opus 5.5 (Opus works at high effort, and a message takes as many steps as the design needs). Chat messages use credits from your plan, and your account shows your balance. MCP connections use no credits: the AI app you connect is paid for by you. Max has them without a monthly count; Maker and Pro have 100 tool calls a month to try them, and so does a free account that contributes its designs and AI sessions. The AI connections panel shows the month's calls.
Each plan has two prices: the contributor's, when you share your designs and AI sessions to improve ProtoJoint's AI, and a higher one when you do not. You choose in Account › Privacy, and the price follows your choice from your next renewal. Under Plan & credits you can set a limit that stops a chat message, and a monthly limit for the chat; neither is set unless you set it. Credits are never bought for you: when they run out, Eleph stops until your plan renews or you buy a pack. The plans are in beta, and their prices may change during it.
What is sent to the AI?
Only while you use it: your request, a description of the design, a picture of the view when Eleph asks for one, and any pictures you attach or markup you send. Pictures are re-encoded in your browser, which drops their EXIF data such as a photo’s GPS position, and our server passes them on to Anthropic with the request without storing them. Over MCP, the tool results, screenshots included, go to the AI app you connected. Anthropic does not train its models on what our server sends it.
Are my designs used to improve ProtoJoint's AI?
On the free plan, the designs you make help improve it, unless you turn that off: in Account › Privacy, or signed out with the note at the foot of the window. Imported files, pictures and meshes stay out, and nothing carries your name. Contributors, on any plan, also share their sessions with the AI; a free account gets 50 AI credits a month for that, and a paid plan its lower price. In the EU, the UK and Quebec nothing is shared until you say so. What is shared is used to test and improve ProtoJoint's AI, its instructions and its tools, never sold; you can delete it any time. The Privacy Policy has the details.
How do I stop it?
Turn off Let AI apps control this tab, and the apps can no longer act on your design. In AI connections you can disconnect any app and revoke any API key; changing or resetting your password disconnects all of them.