B12 MCP Server

The B12 MCP server is about as focused as a connector gets: one tool, no authentication, and a single job — turn a business name and description into a generated website. It runs at https://b12.io/mcp over Streamable HTTP, and because there is no key to provision you can wire it into a client and produce a site preview inside a minute. B12 itself is a website builder aimed at professional-services businesses — law firms, clinics, consultancies, accountants — and the MCP endpoint is the conversational front door to that generator.

What it does

generate_website takes four arguments: the business name, a short description under a thousand characters, an image search keyword, and a punchy hero subtitle. It returns a static preview image rendered above the assistant's reply, plus a link to claim the site. From there the actual editing happens in B12's own editor at b12.io/dashboard — the preview panel in your chat client is not interactive, and the assistant cannot add sections or rewrite copy in place.

Key capabilities

• One-call site generation. Name plus description in, complete multi-section site out, with imagery selected from the keyword you supply.
• No credentials. The endpoint is genuinely open; initialize and tools/list succeed with no headers. That makes it unusually easy to demo.
• Hosted output. Generated sites live on B12 infrastructure, so there is nothing to deploy and no build step.
• Iterate by regenerating. Want a different angle? Call the tool again with a revised description and you get a fresh preview and claim link.
• Guardrails in the tool description. B12 explicitly instructs assistants never to invent a business name or description, which is a sensible constraint that keeps the output tied to what the user actually said.

When to use it

This fits the "someone needs a web presence today" scenario — a freelancer spinning up a first site, an agency mocking up options for a client pitch, or a founder who wants something live before the domain email is even configured. It is a genuinely low-friction path from idea to a page you can look at.

When to reach for something else

Be clear-eyed about the boundaries. There is exactly one tool, and it only creates. You cannot list previously generated sites, edit content, publish, manage a domain, or query analytics through MCP. Everything after generation happens in the B12 web app, and claiming a site means creating a B12 account. If your workflow is "keep a website in sync with a repo" or "programmatically update copy across many pages", this is the wrong shape of integration — you want a headless CMS connector instead.

Practical notes

The tool description is unusually prescriptive about assistant behaviour: gather the real business name and description from the user first, never fabricate them as examples, and do not imply the preview is editable. Assistants that ignore this tend to generate a plausible-looking site for a business that does not exist, which wastes everyone's time. Passing a specific, non-generic image_keywords value also makes a visible difference — "orthodontics" produces better imagery than "services".