AI Coding Assistants (MCP) 3.11.0

copper3d ships a machine-readable index of its own API and guides. Point your AI assistant at it through the copper3d-mcp server and it can look up real signatures instead of inventing them.

Why this exists

copper3d has roughly 1,200 public symbols across 42 modules, plus the hand-written guides in this site. That does not fit in any model's context window, and it is not in any model's training data — so assistants tend to produce plausible-looking calls that do not exist.

The server makes that surface searchable on demand.

It carries no documentation of its own

It reads the index that ships inside the copper3d installed in your project, so what the assistant sees always matches the version you actually depend on — not whatever is newest on this site.

Requirements

bash

npm install copper3d

npm install copper3d

The index lives at node_modules/copper3d/ai-index/. Releases from before 3.11.0 do not contain it.

Working on copper3d itself rather than using it? The server also recognises the copper3d repository, where npm run build puts the index at <repo>/ai-index, so no extra configuration is needed there either.

Setup

Claude Code

The working directory is handled for you, so no path is needed:

bash

# just you, in this project
claude mcp add copper3d -- npx -y copper3d-mcp

# commit to .mcp.json so the team gets it on clone
claude mcp add --scope project copper3d -- npx -y copper3d-mcp

# all your projects
claude mcp add --scope user copper3d -- npx -y copper3d-mcp

# just you, in this project
claude mcp add copper3d -- npx -y copper3d-mcp

# commit to .mcp.json so the team gets it on clone
claude mcp add --scope project copper3d -- npx -y copper3d-mcp

# all your projects
claude mcp add --scope user copper3d -- npx -y copper3d-mcp

Every other client

Other clients start the server with a working directory that is not your project (background), so they have to be told where it is with --project.

Client	Config file	Root key	Needs `--project`
Claude Code	`claude mcp add`, or `.mcp.json`	`mcpServers`	no
Cursor	`.cursor/mcp.json` or `~/.cursor/mcp.json`	`mcpServers`	yes
VS Code / Copilot	`.vscode/mcp.json`	`servers`	yes
Claude Desktop	`%APPDATA%\Claude\claude_desktop_config.json` `~/Library/Application Support/Claude/claude_desktop_config.json`	`mcpServers`	yes
Windsurf	`~/.codeium/windsurf/mcp_config.json`	`mcpServers`	yes

Cursor / Claude Desktop / Windsurf — same shape in all three:

json

{
  "mcpServers": {
    "copper3d": {
      "command": "npx",
      "args": ["-y", "copper3d-mcp", "--project", "/absolute/path/to/your/project"]
    }
  }
}

{
  "mcpServers": {
    "copper3d": {
      "command": "npx",
      "args": ["-y", "copper3d-mcp", "--project", "/absolute/path/to/your/project"]
    }
  }
}

Claude Desktop needs the absolute path in particular: it has no project, and it ignores the cwd field.

VS Code / Copilot — note the different root key, and that ${workspaceFolder} works here:

json

{
  "servers": {
    "copper3d": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "copper3d-mcp", "--project", "${workspaceFolder}"]
    }
  }
}

{
  "servers": {
    "copper3d": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "copper3d-mcp", "--project", "${workspaceFolder}"]
    }
  }
}

The four tools

All read-only.

Tool	What it does
`copper3d_search_api`	Search by name, module, summary or parameter type. Members are indexed on their own, so `aiApplyMask` finds `NrrdTools.aiApplyMask`
`copper3d_get_symbol`	One symbol in full: signature, every parameter, return type, source location, related guides
`copper3d_list_guides`	Table of contents for the hand-written guides
`copper3d_get_guide`	Full markdown of one guide

Options


`--project <path>`	Project directory to find `node_modules/copper3d` under
`COPPER3D_INDEX_PATH`	Skip discovery entirely: point straight at an `ai-index` directory

Without either, the server looks at the MCP workspace roots, then CLAUDE_PROJECT_DIR, then walks up from the working directory.

A failed lookup says so

If it finds no index it reports that and lists every path it tried. It never quietly returns empty results — an assistant reading "no matches" would conclude the library has no API.

Troubleshooting

Symptom	Cause	Fix
Tools never appear in VS Code	Used `mcpServers` in `.vscode/mcp.json`	VS Code calls it `servers`
"AI index was not found"	copper3d not installed, or the client lost the project directory	`npm i copper3d`, then add `--project /abs/path`
Assistant still invents APIs	Server not connected	`claude mcp list`, or your client's MCP panel

What it does not do

Documentation lookup only. copper3d runs in a browser on WebGL; the server is a Node process. It cannot render a scene, execute your code, take screenshots or inspect a live canvas.

Versioning

copper3d-mcp is versioned independently of copper3d. Because it only reads, a copper3d release does not require a new release of the server — update copper3d and the assistant sees the new API straight away.

AI Coding Assistants (MCP) 3.11.0 ​

Why this exists ​

Requirements ​

Setup ​

Claude Code ​

Every other client ​

The four tools ​

Options ​

Troubleshooting ​

What it does not do ​

Versioning ​