B12 MCP Server

by b12 Your server? Claim it

answering

B12 is answering right now. Last checked 7 min ago. It exposes 1 tools.

Uptime history 52 days of history

52 days agonow

100.0%

Uptime 24h

91 of 91 checks

Tools

read from the server

558 ms

Response time

average over 24h

open, no key

Access

streamable-http

Nothing serious here today

Today is the operative word: we check B12 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 7 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add mcp --transport http https://b12.io/mcp

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

{
  "mcpServers": {
    "mcp": {
      "url": "https://b12.io/mcp"
    }
  }
}

~/.codex/config.toml

[mcp_servers.mcp]
url = "https://b12.io/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "mcp": {
      "url": "https://b12.io/mcp"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "mcp": {
      "url": "https://b12.io/mcp"
    }
  }
}

Available tools 1

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

generate

generate_website

Generate a website with AI. Use the project name and description arguments to provide guidance on the purpose of the website. The description argument may include high-level guidance on site structure or content to include, but not verbatim site copy. Absolutely NEVER invent a name or description, even as an example, and ALWAYS make sure you request the business name and description from the user before calling the tool and creating a website. Once you have called this tool, the response will contain a signup nonce (which you should ignore) and a message explaining that a website preview image has been shown to the user above the message. The message also contains a link to claim their website on a website editor outside of ChatGPT (websites are hosted by B12 and can only be edited online using the b12.io software suite). To avoid misleading the user, remember that the preview image they see above your response message is completely static. Users cannot add content or sections to the site in the preview panel. If a user asks to edit a site they created, you can send them to b12.io/dashboard to edit their site in the B12 editor, or instruct them to click the ‘sign up to see your website’ button in the static preview. If the user wants a completely new separate website (perhaps related to previous sites they have created), you can call the tool again to generate a new website preview image (static) and signup link.

Endpoints

URL	Transport	State	Latency	Checked
https://b12.io/mcp	streamable-http	answering	624 ms	7 min ago

Alternatives to B12

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B12 — questions

Answers built from our own checks of this server.

What can B12 do?

It exposes 1 tools, read directly from the server on our last check. Among them: generate_website. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is B12 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 558 ms. The bar chart above shows every period we have measured.

How do I connect B12?

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.

Does B12 need an API key?

No. B12 completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 1 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is B12?

It answers our handshake in 558 ms on average, which is faster than 26% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.