--- a/OrthancServer/Sources/OrthancRestApi/OrthancRestSystem.cpp	Fri Apr 07 22:18:37 2023 +0200
+++ b/OrthancServer/Sources/OrthancRestApi/OrthancRestSystem.cpp	Fri Apr 07 22:54:57 2023 +0200
@@ -1047,6 +1047,31 @@
   }
 
 
+  static void ListAllLabels(RestApiGetCall& call)
+  {
+    if (call.IsDocumentation())
+    {
+      call.GetDocumentation()
+        .SetTag("System")
+        .SetSummary("Get all the used labels")
+        .SetDescription("List all the labels that are associated with any resource of the Orthanc database")
+        .AddAnswerType(MimeType_Json, "JSON array containing the labels");
+      return;
+    }
+
+    std::set<std::string> labels;
+    OrthancRestApi::GetIndex(call).ListAllLabels(labels);
+
+    Json::Value json = Json::arrayValue;
+    for (std::set<std::string>::const_iterator it = labels.begin(); it != labels.end(); ++it)
+    {
+      json.append(*it);
+    }
+    
+    call.GetOutput().AnswerJson(json);
+   }
+
+
   void OrthancRestApi::RegisterSystem(bool orthancExplorerEnabled)
   {
     if (orthancExplorerEnabled)
@@ -1094,5 +1119,7 @@
     Register("/tools/accepted-transfer-syntaxes", SetAcceptedTransferSyntaxes);
     Register("/tools/unknown-sop-class-accepted", GetUnknownSopClassAccepted);
     Register("/tools/unknown-sop-class-accepted", SetUnknownSopClassAccepted);
+
+    Register("/tools/labels", ListAllLabels);  // New in Orthanc 1.12.0
   }
 }