diff --git a/specification/datalake-store/data-plane/Microsoft.DataLakeStore/preview/2015-10-01-preview/filesystem.json b/specification/datalake-store/data-plane/Microsoft.DataLakeStore/preview/2015-10-01-preview/filesystem.json
index 80b5afd54ea0..e0588df749be 100644
--- a/specification/datalake-store/data-plane/Microsoft.DataLakeStore/preview/2015-10-01-preview/filesystem.json
+++ b/specification/datalake-store/data-plane/Microsoft.DataLakeStore/preview/2015-10-01-preview/filesystem.json
@@ -64,7 +64,7 @@
               "format": "file"
             },
             "required": true,
-            "description": "The file contents to include when appending to the file."
+            "description": "The file contents to include when appending to the file.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "appendMode",
@@ -277,14 +277,16 @@
           }
         }
       }
-    },
-    "/webhdfs/v1/{destinationPath}": {
+    }
+  },
+  "x-ms-paths": {
+    "/webhdfs/v1/{destinationPath}?op=CONCAT": {
       "post": {
         "tags": [
           "FileSystem"
         ],
         "operationId": "FileSystem_Concat",
-        "description": "Concatenates the list of source files into the destination file, removing all source files upon success.",
+        "description": "Concatenates the list of source files into the destination file, removing all source files upon success.  This operation has been deprecated, please use operation FileSystem_MsConcat instead.",
         "parameters": [
           {
             "name": "destinationPath",
@@ -329,10 +331,11 @@
               "$ref": "#/definitions/AdlsError"
             }
           }
-        }
+        },
+        "deprecated": true
       }
     },
-    "/webhdfs/v1/{msConcatDestinationPath}": {
+    "/webhdfs/v1/{msConcatDestinationPath}?op=MSCONCAT": {
       "post": {
         "tags": [
           "FileSystem"
@@ -395,7 +398,7 @@
         }
       }
     },
-    "/webhdfs/v1/{listFilePath}": {
+    "/webhdfs/v1/{listFilePath}?op=MSLISTSTATUS": {
       "get": {
         "tags": [
           "FileSystem"
@@ -463,7 +466,7 @@
         }
       }
     },
-    "/webhdfs/va/{getContentSummaryFilePath}": {
+    "/webhdfs/va/{getContentSummaryFilePath}?op=GETCONTENTSUMMARY": {
       "get": {
         "tags": [
           "FileSystem"
@@ -509,7 +512,7 @@
         }
       }
     },
-    "/webhdfs/v1/{getFilePath}": {
+    "/webhdfs/v1/{getFilePath}?op=MSGETFILESTATUS": {
       "get": {
         "tags": [
           "FileSystem"
@@ -555,7 +558,7 @@
         }
       }
     },
-    "/webhdfs/v1/{flushFilePath}": {
+    "/webhdfs/v1/{flushFilePath}?op=APPEND;append=true;flush=true": {
       "post": {
         "tags": [
           "FileSystem"
@@ -621,7 +624,7 @@
         }
       }
     },
-    "/webhdfs/v1/{directFilePath}": {
+    "/webhdfs/v1/{directFilePath}?op=APPEND": {
       "post": {
         "tags": [
           "FileSystem"
@@ -647,7 +650,7 @@
               "format": "file"
             },
             "required": true,
-            "description": "The file contents to include when appending to the file."
+            "description": "The file contents to include when appending to the file.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "offset",
@@ -719,7 +722,7 @@
               "format": "file"
             },
             "required": false,
-            "description": "The file contents to include when creating the file. This parameter is optional, resulting in an empty file if not specified."
+            "description": "The file contents to include when creating the file. This parameter is optional, resulting in an empty file if not specified.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "overwrite",
@@ -834,7 +837,7 @@
         }
       }
     },
-    "/webhdfs/v1/{setAclFilePath}": {
+    "/webhdfs/v1/{setAclFilePath}?op=SETACL": {
       "put": {
         "tags": [
           "FileSystem"
@@ -884,7 +887,7 @@
         }
       }
     },
-    "/webhdfs/v1/{modifyAclFilePath}": {
+    "/webhdfs/v1/{modifyAclFilePath}?op=MODIFYACLENTRIES": {
       "put": {
         "tags": [
           "FileSystem"
@@ -934,7 +937,7 @@
         }
       }
     },
-    "/webhdfs/v1/{removeAclFilePath}": {
+    "/webhdfs/v1/{removeAclFilePath}?op=REMOVEACLENTRIES": {
       "put": {
         "tags": [
           "FileSystem"
@@ -984,7 +987,7 @@
         }
       }
     },
-    "/webhdfs/v1/{defaultAclFilePath}": {
+    "/webhdfs/v1/{defaultAclFilePath}?op=REMOVEDEFAULTACL": {
       "put": {
         "tags": [
           "FileSystem"
@@ -1027,7 +1030,7 @@
         }
       }
     },
-    "/webhdfs/v1/{aclFilePath}": {
+    "/webhdfs/v1/{aclFilePath}?op=REMOVEACL": {
       "put": {
         "tags": [
           "FileSystem"
@@ -1114,7 +1117,7 @@
         }
       }
     },
-    "/webhdfs/v1/{filePath}": {
+    "/webhdfs/v1/{filePath}?op=DELETE": {
       "delete": {
         "tags": [
           "FileSystem"
@@ -1167,7 +1170,7 @@
         }
       }
     },
-    "/webhdfs/v1/{renameFilePath}": {
+    "/webhdfs/v1/{renameFilePath}?op=RENAME": {
       "put": {
         "tags": [
           "FileSystem"
@@ -1220,7 +1223,7 @@
         }
       }
     },
-    "/webhdfs/v1/{setOwnerFilePath}": {
+    "/webhdfs/v1/{setOwnerFilePath}?op=SETOWNER": {
       "put": {
         "tags": [
           "FileSystem"
@@ -1277,7 +1280,7 @@
         }
       }
     },
-    "/webhdfs/v1/{setPermissionFilePath}": {
+    "/webhdfs/v1/{setPermissionFilePath}?op=SETPERMISSION": {
       "put": {
         "tags": [
           "FileSystem"
diff --git a/specification/datalake-store/data-plane/Microsoft.DataLakeStore/stable/2016-11-01/filesystem.json b/specification/datalake-store/data-plane/Microsoft.DataLakeStore/stable/2016-11-01/filesystem.json
index b636e04e8ac5..c7e80ed48e82 100644
--- a/specification/datalake-store/data-plane/Microsoft.DataLakeStore/stable/2016-11-01/filesystem.json
+++ b/specification/datalake-store/data-plane/Microsoft.DataLakeStore/stable/2016-11-01/filesystem.json
@@ -130,7 +130,7 @@
               "format": "file"
             },
             "required": true,
-            "description": "The file contents to include when appending to the file."
+            "description": "The file contents to include when appending to the file.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "appendMode",
@@ -743,7 +743,7 @@
               "format": "file"
             },
             "required": true,
-            "description": "The file contents to include when appending to the file."
+            "description": "The file contents to include when appending to the file.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "offset",
@@ -854,7 +854,7 @@
               "format": "file"
             },
             "required": false,
-            "description": "The file contents to include when creating the file. This parameter is optional, resulting in an empty file if not specified."
+            "description": "The file contents to include when creating the file. This parameter is optional, resulting in an empty file if not specified.  The maximum content size is 4MB.  For content larger than 4MB you must append the content in 4MB chunks."
           },
           {
             "name": "overwrite",