diff --git a/swagger.json b/swagger.json
index 3d564bb1a..f8f570fe9 100644
--- a/swagger.json
+++ b/swagger.json
@@ -1228,6 +1228,13 @@
             "required": true,
             "type": "string"
           },
+          {
+            "external": "external",
+            "in": "query",
+            "description": "Indicates whether mappings to external vocabularies should be listed",
+            "required": false,
+            "type": "boolean"
+          },
           {
             "name": "clang",
             "in": "query",
@@ -1256,6 +1263,9 @@
           "304": {
             "description": "the resource was not modified, so there is no need to retransmit the requested resources"
           },
+          "400": {
+            "description": "URI parameter is missing"
+          },
           "404": {
             "description": "no concept mappings could be found with the requested URI"
           }