eHealth Infrastructure (v2020.4) 

{
  "resourceType" : "OperationDefinition",
  "id" : "ehealth-appointment-toical",
  "text" : {
    "status" : "generated",
    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\"><h2>Export Appointment to iCal</h2><p>OPERATION: Export Appointment to iCal</p><p>The official URL for this operation definition is: </p><pre>http://ehealth.sundhed.dk/fhir/OperationDefinition/ehealth-appointment-toical</pre><div><p>This operation exports the Appointment to an iCal <a href=\"https://tools.ietf.org/html/rfc5545\">RFC-5545</a> format</p>\n</div><p>URL: [base]/Appointment/[id]/$exportAsiCal</p><p>Parameters</p><table class=\"grid\"><tr><td><b>Use</b></td><td><b>Name</b></td><td><b>Cardinality</b></td><td><b>Type</b></td><td><b>Binding</b></td><td><b>Documentation</b></td></tr><tr><td>OUT</td><td>return</td><td>1..1</td><td><a href=\"http://hl7.org/fhir/STU3/bundle.html\">Bundle</a></td><td/><td><div><p>A Binary resource that encapsulates the iCal file.</p>\n</div></td></tr></table><div><p>The iCal file is wrapped inside a Binary resource.</p>\n</div></div>"
  },
  "url" : "http://ehealth.sundhed.dk/fhir/OperationDefinition/ehealth-appointment-toical",
  "name" : "Export Appointment to iCal",
  "status" : "active",
  "kind" : "operation",
  "date" : "2019-02-02",
  "description" : "This operation exports the Appointment to an iCal [RFC-5545](https://tools.ietf.org/html/rfc5545) format",
  "idempotent" : true,
  "code" : "exportAsiCal",
  "comment" : "The iCal file is wrapped inside a Binary resource.",
  "resource" : [
    "Appointment"
  ],
  "system" : false,
  "type" : false,
  "instance" : true,
  "parameter" : [
    {
      "name" : "return",
      "use" : "out",
      "min" : 1,
      "max" : "1",
      "documentation" : "A Binary resource that encapsulates the iCal file. ",
      "type" : "Bundle"
    }
  ]
}