Connect your AI (MCP)

FieldCAD speaks the Model Context Protocol. Connect it to the AI you already pay for — Claude Code, Claude Desktop, the ChatGPT desktop app or Codex — and ask it to work on your documents directly: “add a gyroid infill to the bracket”, “shell the housing to 2 mm and check it's watertight”. Every AI edit is validated and measured by the FieldCAD kernel and lands in the document's history, where you review it in the editor. The AI usage runs onyour subscription — FieldCAD doesn't meter it.

1 · Create an access token

On the Account page, under Connect your AI, create an access token. It is shown once — copy it. The token grants full access to your documents; creating a new one revokes the old.

2 · Connect your client

Claude Code (terminal):

claude mcp add fieldcad https://fieldcad.io/mcp -t http \
  -H "Authorization: Bearer YOUR_TOKEN"

Claude Desktop — add to claude_desktop_config.json (Settings → Developer → Edit Config):

{
  "mcpServers": {
    "fieldcad": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://fieldcad.io/mcp",
               "--header", "Authorization: Bearer YOUR_TOKEN"]
    }
  }
}

ChatGPT desktop app and Codex — Settings → MCP servers → Add server (Streamable HTTP), or add to ~/.codex/config.toml, which both read:

[mcp_servers.fieldcad]
url = "https://fieldcad.io/mcp"
http_headers = { "Authorization" = "Bearer YOUR_TOKEN" }

claude.ai and chatgpt.com (in the browser) need no token: add FieldCAD as a custom connector with the address https://fieldcad.io/mcp (in ChatGPT, developer mode must be on). The app sends you here to log in and allow it; it then shows on your Account page, where you can disconnect it.

3 · Teach it FieldCAD (recommended)

Install the FieldCAD skill so your AI knows the graph semantics, parameter shapes, and common recipes before its first edit:download SKILL.md and save it as~/.claude/skills/fieldcad/SKILL.md for Claude Code, or as~/.codex/skills/fieldcad/SKILL.md for the ChatGPT desktop app and Codex — both pick it up automatically.

What the AI can do

• list_documents / read_graph — see your documents and designs.
• search_blocks / block_doc — look up the block catalog.
• apply_edits — change a design; the batch is atomic, validated and saved as one history entry. The editor that has the design open computes it on your computer, and the AI gets its state back.
• read_state — what your open editor computed: each block's state, its reason when it failed, its value, and the result's volume and bounding box. With no editor open, the AI is told to ask you to open the design: your computer does the computing, never the server.
• view — a picture of the part from a direction the AI chooses, drawn by your editor at a low resolution, each block in its own colour.

Security: the token identifies you and only reaches your own (and public) documents. Revoke it any time by creating a new one on the Account page; apps you allowed in the browser are listed there too, each with its own Disconnect.