About [[MediaWiki:Echo-desc/en]]

That's not accurate.

Echo is an infrastructure in the sense that its primary role is to build something that other extensions can build on. Most extensions, with a few exceptions (SemanticMediaWiki for example) are not primarily intended to be built on – they are the whole product.

It is also intended to supersede existing notifications and messaging techniques in a way that most extensions are not intended to supersede an existing piece of MediaWiki infrastructure.

You're welcome to change the English text, but I think you already know what Echo does, so I don't think this is an issue for translation.