The Jart API and MCP server

1. Get an API key

Sign in, open Account settings and make a key under API keys. Keys come with Pro and up. A key is shown once: copy it into your client’s settings or an environment variable. Jart keeps only a fingerprint of it; revoke it there at any time and it stops working at once. Send it with every call as Authorization: Bearer jart_….

Try it with curl

export JART_API_KEY=jart_…

# Design Facts of a GLB (in metres, the glTF standard)
curl -s "https://thejart.com/api/v1/facts?filename=ring.glb" \
  -H "Authorization: Bearer $JART_API_KEY" \
  --data-binary @ring.glb

# The cast check of an STL drawn in millimetres, in sterling silver
curl -s "https://thejart.com/api/v1/cast-check?filename=ring.stl&metal=silver" \
  -H "Authorization: Bearer $JART_API_KEY" \
  --data-binary @ring.stl

# Is this the approved file? (the id from the approval's /a/ link)
curl -s "https://thejart.com/api/v1/verify?approval=$APPROVAL_ID&filename=ring.glb" \
  -H "Authorization: Bearer $JART_API_KEY" \
  --data-binary @ring.glb

# Send the approved version to your caster (a retry returns the same link)
curl -s "https://thejart.com/api/v1/casts" \
  -H "Authorization: Bearer $JART_API_KEY" \
  -H "Content-Type: application/json" \
  -d "{\"approval_id\":\"$APPROVAL_ID\",\"caster\":\"Bangkok Cast\"}"

# What 3.2 g of metal casts at with each of your casters
curl -s "https://thejart.com/api/v1/casters?grams=3.2" -H "Authorization: Bearer $JART_API_KEY"

Units. GLB is read in metres and STL and OBJ in millimetres, as in the studio. If a file is drawn in another unit, add units=mm|cm|m|in or scale= (millimetres per file unit); an answer that looks the wrong size carries a note saying so. Metal and stones are told apart the way the studio’s Auto assign does it, from part names (“Band 18k”, “Diamond 1.5”) and then glass-like materials; metal= sets every metal part to one of 16 alloys (for example gold14, platinum, silver). An STL has no part names, so it is measured as metal only.

Connect your assistant

Claude Code

claude mcp add --transport http jart https://thejart.com/api/v1/mcp \
  --header "Authorization: Bearer $JART_API_KEY"

Claude Desktop

Claude Desktop’s config file starts local servers, so connect through mcp-remote (needs Node.js). In Settings → Developer → Edit config, add:

{
  "mcpServers": {
    "jart": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://thejart.com/api/v1/mcp",
        "--header",
        "Authorization:Bearer jart_…"
      ]
    }
  }
}

Restart Claude Desktop; the Jart tools appear under the tools menu. Where your organisation has custom connectors with request headers, add https://thejart.com/api/v1/mcp as a custom connector with the header Authorization: Bearer jart_… instead.

Cursor

In ~/.cursor/mcp.json or a project’s .cursor/mcp.json:

{
  "mcpServers": {
    "jart": {
      "url": "https://thejart.com/api/v1/mcp",
      "headers": {
        "Authorization": "Bearer ${env:JART_API_KEY}"
      }
    }
  }
}

VS Code

In .vscode/mcp.json; VS Code asks for the key once and stores it:

{
  "inputs": [
    {
      "type": "promptString",
      "id": "jart-key",
      "description": "Jart API key",
      "password": true
    }
  ],
  "servers": {
    "jart": {
      "type": "http",
      "url": "https://thejart.com/api/v1/mcp",
      "headers": {
        "Authorization": "Bearer ${input:jart-key}"
      }
    }
  }
}

ChatGPT

ChatGPT connects to MCP servers that sign in with OAuth or need no sign-in, and Jart’s uses keys, so it does not connect to ChatGPT yet. Sign-in with your Jart account is planned.

Then ask

“Here is ring.glb: what does it weigh in 14k and platinum, and what ring size is it?” · “Is this file ready to cast? My caster wants 0.8 mm walls.” · “Is this the version my client approved on Jart?” · “Send the approved Solitaire for Mia to Bangkok Cast.” · “What will 3.2 g cast at with Bangkok Cast?” · “Is this ring photo verified from CAD? thejart.com/v/…”

Your files and your data

Files you send are measured in memory and never stored: nothing is saved to your projects and nothing is kept after the answer. Jart keeps your keys’ names and fingerprints and a count of calls per key and day for 90 days, which you can see in Account settings, download with your data and delete with your account (privacy policy). Every figure is an estimate from the file’s mesh: casting adds sprue and loss, alloys vary by a few percent, and carat comes from each stone’s volume. Verify before casting.