changes for json

Author: ash2017

articles/event-grid/event-schema-iot-hub.md

@@ -176,7 +176,7 @@ For **Device Telemetry** IoT Hub event, the data object contains the device-to-c
 | -------- | ---- | ----------- |
 | body | string | The content of the message from the device. |
 | properties | string | Application properties are user-defined strings that can be added to the message. These fields are optional. |
-| system properties | string | [System properties](../iot-hub/iot-hub-devguide-routing-query-syntax.md#system-properties) help identify contents and source of the messages. |
+| system properties | string | [System properties](../iot-hub/iot-hub-devguide-routing-query-syntax.md#system-properties) help identify contents and source of the messages. Device telemetry message must be in a valid JSON format with the contentType set to JSON and contentEncoding set to UTF-8 in the message system properties. If this is not set, then IoT Hub will write the messages in base 64 encoded format.  |
 
 For **Device Created** and **Device Deleted** IoT Hub events, the data object contains the following properties:
 

articles/iot-hub/iot-hub-devguide-messages-d2c.md

@@ -34,7 +34,7 @@ You can use standard [Event Hubs integration and SDKs](iot-hub-devguide-messages
 
 ### Azure Blob Storage
 
-IoT Hub supports writing data to Azure Blob Storage in the [Apache Avro](https://avro.apache.org/) format as well as in JSON format. The capability to encode JSON format is generally available in all regions in which IoT Hub is available. The default is AVRO. The encoding format can be only set when the blob storage endpoint is configured. The format cannot be edited for an existing endpoint. When using JSON encoding, you must set the contentType to JSON and contentEncoding to UTF-8 in the message [system properties](iot-hub-devguide-routing-query-syntax.md#system-properties). You can select the encoding format using the IoT Hub Create or Update REST API, specifically the [RoutingStorageContainerProperties](https://docs.microsoft.com/rest/api/iothub/iothubresource/createorupdate#routingstoragecontainerproperties), the Azure portal, [Azure CLI](https://docs.microsoft.com/cli/azure/iot/hub/routing-endpoint?view=azure-cli-latest), or the [Azure Powershell](https://docs.microsoft.com/powershell/module/az.iothub/add-aziothubroutingendpoint?view=azps-1.3.0). The following diagram shows how to select the encoding format in the Azure portal.
+IoT Hub supports writing data to Azure Blob Storage in the [Apache Avro](https://avro.apache.org/) format as well as in JSON format. The capability to encode JSON format is generally available in all regions in which IoT Hub is available. The default is AVRO. The encoding format can be only set when the blob storage endpoint is configured. The format cannot be edited for an existing endpoint. When using JSON encoding, you must set the contentType to JSON and contentEncoding to UTF-8 in the message [system properties](iot-hub-devguide-routing-query-syntax.md#system-properties). If this is not set, then IoT Hub will write the messages in base 64 encoded format. You can select the encoding format using the IoT Hub Create or Update REST API, specifically the [RoutingStorageContainerProperties](https://docs.microsoft.com/rest/api/iothub/iothubresource/createorupdate#routingstoragecontainerproperties), the Azure portal, [Azure CLI](https://docs.microsoft.com/cli/azure/iot/hub/routing-endpoint?view=azure-cli-latest), or the [Azure Powershell](https://docs.microsoft.com/powershell/module/az.iothub/add-aziothubroutingendpoint?view=azps-1.3.0). The following diagram shows how to select the encoding format in the Azure portal.
 
 ![Blob storage endpoint encoding](./media/iot-hub-devguide-messages-d2c/blobencoding.png)
 

articles/iot-hub/iot-hub-event-grid.md

@@ -67,7 +67,7 @@ The following example shows the schema of a device connected event:
 
 ### Device Telemetry schema
 
-The following example shows the schema of a device telemetry event: 
+Device telemetry message must be in a valid JSON format with the contentType set to JSON and contentEncoding set to UTF-8 in the message [system properties](iot-hub-devguide-routing-query-syntax.md#system-properties). If this is not set, then IoT Hub will write the messages in base 64 encoded format. The following example shows the schema of a device telemetry event: 
 
 ```json
 [{