In the demo, it can analyze plain text But in the API reference all REST APIs require url. And they don't seem to support analyze text directly. I tried to use text in a POST form anyway. But I got error.
{
"status": "ERROR",
"statusInfo": "invalid-url"
}
This is more a documentation issue, than a coding issue. In the documentation you will see three buttons. Select the Text one to get the documentation on Text calls.