Marvel-agent plugin doesn't function on elasticsearch 2.1.1

After installing marvel-agent (default settings) and going to <host>:9200/_plugin/marvel-agent/ just gives me a blank page. It's the same response when entering any other made up url, e.g.: <host>:9200/_plugin/something-non-existing/

I've checked the plugin is installed, and ES is actually reporting back that it's installed. Doing: <host>:9200/_nodes?plugin=true shows:

plugins: [
{
name: "head",
version: "master",
description: "head - A web front end for an elastic search cluster",
url: "/_plugin/head/",
jvm: false,
site: true
},
{
name: "license",
version: "2.1.1",
description: "Internal Elasticsearch Licensing Plugin",
jvm: true,
classname: "org.elasticsearch.license.plugin.LicensePlugin",
isolated: false,
site: false
},
{
name: "marvel-agent",
version: "2.1.1",
description: "Elasticsearch Marvel Agent",
jvm: true,
classname: "org.elasticsearch.marvel.MarvelPlugin",
isolated: false,
site: false
}
]

Does the fact that marvel-agent doesn't show an url-property indicate something here? I.e.: plugin head has an url (and is available there), but marvel-agent doesn't.

In fact, going into plugins/marvel-agent I'm seeing no _site directory, which according to the docs is to be loaded on the specified url-endpoint.

Elasticsearch version from the same url above: 2.1.1

Anyone can tell me what's up?

The Marvel 2 user interface is provided as a Kibana 4 plugin, not an Elasticsearch site plugin. There are instructions for how to install this on the downloads page.

Indeed, I recommend the Getting Started Guide, which will walk you through the whole process:

https://www.elastic.co/guide/en/marvel/current/getting-started.html