Azure Logic Apps-The template language function ‘json’ parameter is not valid.

This is a follow up from my original blog post Azure Logic Apps–Parsing JSON message from service bus

If you see the following error from a Logic App using Service Bus trigger:

{"code":"InvalidTemplate","message":"Unable to process template language expressions in action 'Next_action' inputs at line '1' and column '11': 'The template language function 'json' parameter is not valid. The provided value 'eydlbWFpbCcgOiAndGVzdEB0ZXN0LmNvbSd9' cannot be parsed: 'Unexpected character encountered while parsing value: e. Path '', line 0, position 0.'. Please see for usage details.'."}

It’s because messages that from service bus topic triggers are now presented as base 64 encoded messages rather than plain text.  Fortunately the fix is straightforward, Logic Apps give you a decodeBase64 function that you can use in the Logic App. 

You need to switch the Logic App to to code view, and use the decodeBase64 function before parsing the json.  So


becomes (note the call to decodeBase64 before the call to json):


Azure Logic Apps-Service Bus connector not automatically triggering?

By default logic apps will be set to trigger every 60 minutes which, if you are not aware, may lead you to thinking that your logic app isn’t working at all!

As Logic Apps are preview there are some features that are not available through the designer yet, but you can do a lot through the Code view.

In this instance you can set the frequency to Second, Minute, Hour, Day, Week, Month or Year.  For a frequency of every minute it is required to be on a standard service plan or better. If your service plan doesn’t allow the frequency you will get an error as soon as you try and save the logic app.  Here’s what I set to have it run every minute.

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More information can be found at

Azure Logic Apps–Parsing JSON message from service bus

What I want: When the logic app trigger receives a JSON formatted message from Azure Service Bus topic, I want to send a notification to the “email” field.  My sample message structure looks like this:


What happens: Because a message received on service bus doesn’t have a predefined format – it could be JSON, XML, or anything else – so Logic Apps doesn’t know the structure of the message.  So in the designer, it looks like:


Which is great, but it just dumps out the entire object, and not the email field that I need.

How to fix it: Fortunately the fix is pretty easy, basically you need

1) Select the Content output (above), you are going to edit this value.

2) Switch over to ‘Code view’ and manually type the expression (below).

If you haven’t used it before, code view can be found in the toolbar:


Once you are in the code view, scroll down to the connector you are interested in. You will see the expression for the trigger body. This is the entire message received from the trigger, basically.


You need to modify this to parse the entire message using the ‘json’ function, then you can access it’s typed fields.

If you have ever used JSON.parse (or any object deserialization in pretty much any language for that matter) this concept should be familiar to you.  When I was done I ended up with:


I’ve broken the entire segment into two parts, a) parses the content and b) accesses the ‘email’ field of the parsed JSON object.

Hope this helps someone!


Update: if you are seeing an error when trying to parse see my new blog post Azure Logic Apps-The template language function ‘json’ parameter is not valid.