[Feature request] Allow MCP Gateway to proxy existing MCP Servers

[eximius313]

It would be great if MCP Gateway could act as a proxy for already existing MCP Servers.

Use case / Example:
I’m using Home Assistant MCP.
Currently, they recommend using sparfenyuk/mcp-proxy as an example. However, I’d much prefer to use Docker MCP Gateway as a centralized manager.

Proposal:
Please make it possible to add arbitrary remote servers (e.g. http://localhost:8123/mcp_server/sse) as a source for MCP Gateway.

[slimslenderslacks]

Thanks @eximius313. We're in the middle of merging support for this.

One of the challenges today is that we are on the verge of having an official MCP registry that will allow us to register remote servers and then import them into the Docker mcp gateway.

For example, a server definition like:

{
  "name": "io.modelcontextprotocol.anonymous/remote-mcp-example",
  "description": "example of an arbitrary remote server",
  "repository": {
    "url": "https://github.com/example/hybrid-mcp",
    "source": "github",
    "id": "klm012no-pqrs-3456-tuvw-xyz789abcdef"
  },
  "version": "1.5.0",
  "remotes": [
    {
      "type": "streamable-http",
      "url": "https://mcp.anonymous.modelcontextprotocol.io/http"
    }
  ],
}

Will get a url like https://registry.modelcontextprotocol.io/v0/servers/{id} which you'll be able use with these commands:

docker mcp catalog create custom-catalog
docker mcp catalog import custom-catalog --mcp-registry https://registry.modelcontextprotocol.io/v0/servers/{id}
docker mcp server enable io.modelcontextprotocol.anonymous/remote-mcp-example

# and finally
docker mcp gateway run

Since the Official MCP registry is providing a standard format for defining servers, it seems like this could become a popular way to define existing remotes and then proxy them.

Catalogs today

Even without using the Official Registry, we can still define custom catalogs and add add remotes. For example, a very similar flow to above would be:

docker mcp catalog create custom-catalog

# now go to ~/.docker/mcp/catalogs/custom-catalog.yaml and edit it with the entry below

docker mcp server enable myremote
docker mcp gateway run

But you'd have to add the myremote entry to you custom catalog like this:

name: custom-catalog
displayName: custom-catalog
registry:
  myremote:
    name: io.github.slimslenderslacks/remote
    description: remote example
    remote:
      url: http://localhost:8123/mcp_server/sse
      transport_type: sse

And that will work with the latest version of the gateway. If you want to build your own version of docker-mcp (https://github.com/docker/mcp-gateway?tab=readme-ov-file#install-as-docker-cli-plugin), you can run the official registry example today. The only problem is that official mcp registry project is still in preview (https://github.com/modelcontextprotocol/registry)

[eximius313]

@slimslenderslacks

1. I believe that instead of ~/.docker/mcp/catalogs/custom-catalog.json you ment ~/.docker/mcp/catalogs/custom-catalog.yaml?
2. Why name: io.github.slimslenderslacks/remote? or can it be just name: my remote's name?
3. Adding it via catalog works fine. But I was just wondering - if I already have the URL, could it be possible to use CLI directly, e.g.:

$ docker mcp catalog add-remote myCatalog --url http://localhost:8123/mcp_server/sse --transport sse

?

[slimslenderslacks]

1. Yes, I meant ~/.docker/mcp/catalogs/custom-catalog.yaml!
2. So, for the case of Official MCP registry support, the name has to be namespaced (the Official Registry naming standards require that publishers prove that they own any namespace that they publish into). But if you're adding the entry yourself (not importing from the MCP registry) then you can just use your remote's name.
3. I agree that we probably now have all the pieces to build a small script that would do exactly what you're proposing. Because you're talking about composing

docker mcp catalog create myCatalog
# now inject a remote for http://localhost:8123/mcp_server/sse with name X
docker mcp server enable X

Is that what you mean?

[eximius313]

Is that what you mean?

exactly ;)