FabTally MCP Server

The first MCP server for real FDM 3D-printing slicing, quoting, and DFM / printability analysis. Every other 3D-printing MCP just drives a printer (OctoPrint, Bambu). None of them slice, quote, or run design-for-manufacturability checks — FabTally does.

It fronts the FabTally agent API (https://fabtally.com), which runs OrcaSlicer against 12 calibrated FDM printer profiles and 12 filament materials, and exposes it as MCP tools so any MCP-capable agent (Claude Desktop, Cursor, custom agents) can discover and call it.

• Free tools (discovery + a printability preview) work with no payment.

• Paid tools settle over x402 (USDC on Base). With no payment supplied they return the x402 challenge (price, network, asset, payTo) so the calling agent knows the cost and can pay and retry.

• This server holds no private key and persists no models. It only relays calls to https://fabtally.com/agent/...; uploaded models are streamed to the slicer, never stored.

Tools

Related MCP server: PrusaMCP

The 12 printers

Materials: pla, pla-cf, petg, petg-cf, abs, abs-cf, asa, asa-cf, nylon, pc, pet, tpu (PLA/PETG/ABS/ASA + carbon-fiber variants, Nylon, PC, PET, TPU). list_printers always returns the authoritative live list.

Supplying a model file

MCP tools can't take raw file uploads, so every model-consuming tool accepts the model two ways — pick one:

• model_url — a public https URL to an STL / 3MF / OBJ / PLY / STEP file. The server fetches it. (Try https://fabtally.com/sample-cube-20mm.stl.)

• model_base64 + filename — the raw file bytes, base64-encoded, plus a filename (e.g. "cube.stl") so the file type is known.

Example tool calls

// 1) Discover printers/materials/pricing (free)
{ "name": "list_printers", "arguments": {} }

// 2) Free printability check on a hosted model
{ "name": "check_printability",
  "arguments": { "model_url": "https://fabtally.com/sample-cube-20mm.stl" } }

// 3) Full paid DFM report (returns x402 challenge unless x_payment is supplied)
{ "name": "check_printability",
  "arguments": { "model_url": "https://example.com/bracket.stl",
                 "full": true, "printer": "bambu-p1s", "material": "petg" } }

// 4) Price quote, base64 model, 10 parts
{ "name": "get_print_quote",
  "arguments": { "model_base64": "<...>", "filename": "part.stl",
                 "material": "pla", "quantity": 10 } }

// 5) Least-support orientation (paid $0.02)
{ "name": "optimize_orientation",
  "arguments": { "model_url": "https://example.com/handle.stl", "printer": "prusa-mk4" } }

// 6) Slice with a preview PNG (paid tier $0.01)
{ "name": "slice_model",
  "arguments": { "model_url": "https://example.com/gear.stl",
                 "printer": "voron-24-350", "material": "abs",
                 "quality": "standard", "include_preview": true } }

Install

cd fabtally-mcp-server
npm install

Run (stdio — primary)

node index.js
# or, after `npm install -g .`:  fabtally-mcp

The server speaks MCP over stdio. Point your MCP client at it.

Claude Desktop / MCP client config

{
  "mcpServers": {
    "fabtally": {
      "command": "node",
      "args": ["/absolute/path/to/fabtally-mcp-server/index.js"]
    }
  }
}

Run (Streamable HTTP — optional)

MCP_HTTP_PORT=8103 node http.js
# POST MCP JSON-RPC messages to http://127.0.0.1:8103/mcp   (stateless)

Configuration

How paid calls work (x402)

1. Call a paid tool (or check_printability with full: true) without x_payment. You get { "payment_required": true, "http_status": 402, "challenge": { ... } } containing the x402 accepts entry (scheme exact, network eip155:8453 = Base, asset USDC, atomic amount, payTo).

2. Build an x402 payment authorization (EIP-3009 transferWithAuthorization to payTo) for that entry using your x402 client / wallet.

3. Call the tool again with the resulting token in the x_payment argument. The server forwards it as the X-PAYMENT header and returns the actual result.

Free discovery is always at GET https://fabtally.com/agent/overview; the OpenAPI contract at https://fabtally.com/openapi.json; x402 discovery at https://fabtally.com/.well-known/x402.

Test

node smoke-test.mjs   # lists tools, calls list_printers + check_printability, checks paid 402s

License

MIT · Sunstone Soft · https://fabtally.com