MCP Servers (Per-App)

Attach external Model Context Protocol servers to a specific app so the AI building the app can call your custom tools. Sibling to /docs/mcp, which covers calling GenMB from external MCP clients.

Adding MCP servers to an app requires a Pro or Business plan.

Most people never need this page

This is only for connecting your own custom tools to the AI that builds your app. If you are not running an MCP server of your own, you can ignore this - just describe what you want in chat and GenMB builds it with its built-in tools. This page is for developers who want to plug in extra tools.

Adding a Server

Attaching an MCP server gives the AI building your app extra tools to call - live travel data, an internal API, a domain-specific search - so it can pull in things it could not otherwise reach while generating or refining your app.

Open the MCP panel

From the app editor sidebar, open MCP. You will see a list of any servers already attached.

Click Add Server

Provide a name, the server URL (HTTPS), and optional custom headers (for auth). The transport (SSE / HTTP) is detected.

Verify the connection

GenMB makes a tool-discovery call. If the server is reachable and responds with a valid tool list, the server is saved and the tools become available to the code generator and chat.

The tool discovery happens once on add and again whenever you click Refresh. Tools added on the server later require a Refresh to be picked up.

Auth Headers

Custom headers are stored per-server and sent on every tool call. The most common pattern:

Authorization: Bearer YOUR_SECRET_TOKEN
X-Workspace-Id: ws_123

Headers are stored on the app document. Anyone with editor access to the app can see and edit them. For secrets that should not be visible to collaborators, gate the server with a short-lived token rotated outside of GenMB.

How the Generator Uses It

During generation and chat refinement, the AI sees the union of GenMB's built-in tools and the tools exposed by attached MCP servers. When a tool call would help (e.g. fetching real data, calling a domain-specific API), the AI invokes it; the result flows back into the generation context.

Give tools descriptive names and detailed schemas on the server side. The clearer the tool descriptions, the better the AI's judgment about when to call them.

For external clients (Claude Desktop, Cursor) calling GenMB's own MCP server, see the MCP Integration page.

Limits

Cap on attached servers per app (validated server-side when adding).
Server URL must be HTTPS and publicly reachable.
Tool discovery + invocation must respect GenMB's per-app rate limits (200 req / min / IP applies to outbound calls too).
Pro or Business plan required to add a server. Listing existing servers is allowed on any plan.

FAQs

How is this different from /docs/mcp?▾

The MCP Integration page covers connecting external AI tools (Claude Desktop, Cursor) to GenMB so they can act on your apps. This page covers the other direction: attaching external MCP servers to a specific app so the AI building that app can call them.

What can an attached MCP server do?▾

It exposes tools to GenMB's code generator and chat refinement loops. A travel-search MCP server, for example, would let the generator call live travel data while building or refining your app. Tools are discovered automatically when the server is added.

Where does the MCP server need to run?▾

On a publicly reachable URL with HTTPS. SSE (Server-Sent Events) and HTTP transports are both supported. Self-hosted or third-party hosted are both fine, as long as the URL is reachable from GenMB.

Can I gate access with a key?▾

Yes. When you add the server, include a custom header (commonly Authorization with a Bearer token). The header is sent on every tool call from GenMB.

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