Name: Three.js 3D Viewer MCP Server
Availability: InStock
Author: Three.js 3D Viewer

Question 1

Is the Three.js 3D Viewer a product I can rely on?

Accepted Answer

No. It is a reference implementation the Model Context Protocol project publishes to demonstrate MCP Apps, hosted at example-server.modelcontextprotocol.io and shipped as one of twenty-six examples in the ext-apps repository. It carries no availability commitment, no service level and no support channel beyond the repository issue tracker. Treat it as a demonstration you can read, run locally and learn from.

Question 2

Does the Three.js MCP server need an account or an API key?

Accepted Answer

No. We opened an anonymous handshake against the endpoint on 2026-08-18 and the server returned both tool definitions, its capability block and its resource listing without any credential. That contradicts the directory entry, which records is_authless as false and an auth posture of auth_required. The wire behaviour is what a client actually meets, so no sign-in is needed.

Question 3

Why does Anthropic's directory list no tools for this connector?

Accepted Answer

The listing is empty and the server is not. Anthropic's directory records tool_names as an empty array, while a live tools/list on 2026-08-18 returned two tools, show_threejs_scene and learn_threejs. This is a total absence rather than a partial mismatch, so nothing in the listing describes the surface. Read the tool names from the handshake, never from the directory entry.

Question 4

Where does the 3D scene actually render, and what runs the code?

Accepted Answer

In your own MCP client, not on the server. The server declares a resources capability and serves one HTML widget at ui://threejs/mcp-app.html with MIME type text/html;profile=mcp-app, the MCP Apps marker. The show_threejs_scene tool points at that same URI, so a supporting client loads the widget and executes your JavaScript against a WebGL canvas locally.

Question 5

What does the learn_threejs tool return?

Accepted Answer

A documentation string, not a live lookup. The server source shows learn_threejs takes no parameters and returns a fixed Three.js reference bundled into the server: the list of available globals, template scenes for transparent and solid backgrounds, a rotating cube example, an interactive OrbitControls example, and tips on materials, lighting and animation. It never queries the network.

Question 6

Is the Three.js connector safe to call?

Accepted Answer

Both tools ship without safety annotations, so the server asserts nothing either way. Neither carries readOnlyHint nor destructiveHint — the fields are absent, not set false. In practice show_threejs_scene runs your JavaScript inside the client widget and learn_threejs returns a static string, but that reading comes from the published source rather than from a declaration on the wire.

Question 7

Can I use the Three.js viewer outside Claude?

Accepted Answer

The directory lists Claude only, and the widget needs MCP Apps support. Anthropic records works_with as claude alone, so nothing else is listed as compatible. Any MCP client can complete the handshake and call both tools, but a client that does not implement the MCP Apps extension gets text back instead of a rendered scene, which removes the point of the server.

Question 8

Why does the directory link to the PDF server's README?

Accepted Answer

It is a wrong link in the listing. Anthropic's directory publishes the documentation URL as the pdf-server README inside the ext-apps repository, which documents a different example entirely. The correct file is the threejs-server README in the same repository. We confirmed both URLs return 200 on 2026-08-18, so the bad link resolves cleanly to the wrong server's documentation.

Three.js 3D Viewer

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