I am playing around with the API of Centova v3 to see what is possible and the playlist method looks very useful for managing playlists remotely.

The problem is I always get an error response saying "Must specify a valid action" and I don't know why.

Request:
http://example.com:2199/api.php?f=json&a[username]=username&a[password]=password&xm=server.playlist&action=list

Response:
{
  "type": "error",
  "response": {
    "message": "Must specify a valid action"
  }
}

Figured it out. Parameters need to be passed to the API like this: &a[action]=list