The 3D printing MCP server: design, export and slice from any AI assistant

Set it up in your client

Claude (claude.ai, Desktop, phone)

Customize, Connectors, then search for SpeakCAD, or +, Add custom connector, and paste https://speakcad.com/api/mcp; this link opens the dialog already filled in. Step by step.

ChatGPT

Settings, Plugins, search for SpeakCAD, or in developer mode + with https://speakcad.com/api/mcp and OAuth. Step by step.

Claude Code

bash
claude mcp add --transport http speakcad https://speakcad.com/api/mcp

Then /mcp in a session to sign in.

Cursor

In ~/.cursor/mcp.json (or .cursor/mcp.json in a project):

json
{
  "mcpServers": {
    "speakcad": { "url": "https://speakcad.com/api/mcp" }
  }
}

VS Code

In .vscode/mcp.json:

json
{
  "servers": {
    "speakcad": { "type": "http", "url": "https://speakcad.com/api/mcp" }
  }
}

Any other client

Streamable HTTP transport, OAuth 2.1 with dynamic client registration: the client finds SpeakCAD's authorization server from the 401 it gets on the first call, registers itself and opens the sign-in page. No API key, no client secret. For the slicer server, https://speakcad.com/api/mcp/slicer, there is no authentication at all.

Two servers

Every tool has a title and annotations that say whether it only reads or writes to the account (nothing is ever deleted: a change is a new version), so a client can ask before a call that spends credits.

The 3D view in the conversation

The design, part and slicing tools point to an MCP App: in hosts that render them (Claude, ChatGPT) the part appears in a card, in 3D, while it is designed and after, with its named dimensions as number fields, the STL and 3MF buttons, and a slicer for the person's printer. In hosts without apps, every tool still returns text: the status, the size, the dimensions and the links.

Why a CAD tool behind the model

A language model can write OpenSCAD or describe a shape, and it cannot compile, look at or print-check what it wrote. The SpeakCAD server gives it a CAD loop: a parametric program written by SpeakCAD's AI with design rules for printable parts, compiled into exact geometry, FDM rules applied (wall thickness, clearances of 0.2 to 0.4 mm where parts mate, a flat base), a watertight mesh out, and G-code from the unmodified OrcaSlicer with each printer's bundled profile. The assistant keeps the conversation; the tools keep the geometry honest.

Good for agents too

A coding agent wiring up an ESP32 or a Raspberry Pi can ask for the enclosure in the same session: "design a case for this board, 2 mm walls, USB-C on the short side, M3 standoffs on its mounting holes". The part lands in the person's SpeakCAD models with a link to the editor, and the STL or G-code comes back as a link.

Limits

• Functional parts, not sculptures. Brackets, enclosures, mounts, adapters, organizers. For figurines, a generative mesh tool fits better.
• STL, 3MF and G-code. No STEP and no .scad download.
• One model per slice, standard profiles. No multi-colour painting, modifiers or custom G-code; a desktop slicer stays the tool for those.
• Files never travel through the model. Uploads for slicing go from the person's browser to the slicer; downloads are links.

What it costs

Connecting is free. The main server spends the signed-in account's credits at the site's prices: 2 credits per AI request (the first design or a change), 10 credits per STL or 3MF download (a paid design re-downloads free after small fixes), and 5 credits more for G-code sliced for your printer (included in Pro and Unlimited). Unlimited also includes the requests and downloads. Typing new dimensions in the card and turning the part around in 3D spend nothing. The slicer server gives 3 free slices a day in Claude and ChatGPT without an account; after that, the online slicer gives every account 1 free slice, its first (a free account, no card). After that, a slice uses one slice from a Slicer pack (20 slices for $3, once, never expire) or 5 credits, and slicing is included in Pro and Unlimited. Re-slicing the same file with other settings within 10 minutes is free.