R3 MCP Server

by r3js Your server? Claim it

answering

R3 is answering right now. Last checked 13 min ago.

Build interactive 3D web apps — scenes, physics, audio and music — from composable components.

Uptime history 20 days of history

20 days agonow

100.0%

Uptime 24h

91 of 91 checks

—

Tools

hidden behind auth

270 ms

Response time

average over 24h

API key

Access

streamable-http

Nothing serious here today

Today is the operative word: we check R3 every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 13 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add r3 --transport http https://mcp.r3js.org/mcp

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "r3": {
      "url": "https://mcp.r3js.org/mcp"
    }
  }
}

~/.codex/config.toml

[mcp_servers.r3]
url = "https://mcp.r3js.org/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "r3": {
      "url": "https://mcp.r3js.org/mcp"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "r3": {
      "url": "https://mcp.r3js.org/mcp"
    }
  }
}

This endpoint answered with an authorization challenge. The server is running, but you need an API key from its owner to call it.

Endpoints

URL	Transport	State	Latency	Checked
https://mcp.r3js.org/mcp	streamable-http	needs key	450 ms	13 min ago

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R3 — questions

Answers built from our own checks of this server.

Why is there no tool list for R3?

The server answered our handshake with an authorization challenge, so it is running — but it will not describe its tools to an anonymous client. To see them you need to connect with your own credentials. We record it as alive, not as broken: 100.0% of checks in the last 24 hours got a reply.

Is R3 working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 270 ms. The bar chart above shows every period we have measured.

How do I connect R3?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address. You will need your own key: it refuses anonymous clients.

Does R3 need an API key?

Yes. Every time we knock, R3 answers with an authorization challenge instead of its tool list — that is how we know it is running and gated rather than broken. Bring your own credentials and it will talk.

How fast is R3?

It answers our handshake in 270 ms on average, which is faster than 54% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.