It seems like Segment expects the library in all events to be set in the context but this Erlang client only sends the app definition, as you can see in the block below from a track event captured with the debugger feature of Segment.io:

{
  "context": {
    "app": {
      "name": "esegment",
      "version": "0.11"
    },
    "library": {
      "name": "unknown",
      "version": "unknown"
    }
  },
...

This issue is more of a question: should esegment have the default context function defining the library instead of app, or should both be defined?