[Limitation]PowerAutomate: Unable to use Custom Connector with actions having parameterized GET requests. Error: “Fix Invalid expression(s) for the input parameter(s) of operation ‘ActionName'”.

Recently, I was working on creating a custom connector that has got one action which is a GET request and accepts parameters. The purpose was to use this custom connector in Power Automate which could then have been executed on demand or create/update of record.

Below is the definition of custom connector:

And here’s the request details(Used Import from sample to construct this):
Verb: GET
URL: CalculateRollupField(Target=@target,FieldName=@fieldName)?@target={‘@odata.id’:’accounts(96ca73be-14e5-eb11-bacb-0022481016fb)’}&@fieldName=’new_noofcontacts’

I have passed 2 parameters in the URL @target and @fieldName. So, finally the request looks like as shown below:

Then I tested the custom connector and it was working fine. It refreshed the roll up field as expected.

So, I thought of using it in Power Automate so that I can refresh the roll up field on create/update of a child record as shown below:

When I started putting any value for any of the parameter the Power Automate started complaining with error: “Fix Invalid expression(s) for the input parameter(s) of operation <Action Name>”. It didn’t allow me to save. The reason of the issue is the parameter name starts with “@” which is a special character in Power Automate.

I tried to pass value to those parameters in different ways but none of them worked. Finally, I raised a support request with Microsoft to find out if there is any workaround. However, there is none at the moment and Microsoft acknowledged that this is a limitation.

As per Microsoft, “This is a design behavior from flow, where flow designer does not allow parameters containing special character @ in their name.”

As per Microsoft, The product group has been actively working on the code fix, and planning to complete the process at the 1st week of September.

I’ll keep this post updated as soon as I hear back from Microsoft on this. Hope it helps !!

4 thoughts on “[Limitation]PowerAutomate: Unable to use Custom Connector with actions having parameterized GET requests. Error: “Fix Invalid expression(s) for the input parameter(s) of operation ‘ActionName'”.

  1. Hi Ajit,
    Thanks for this article. I am trying to achieve same and getting same error. As you mentioned that MS will try to resolve this by Sep 1st week but it doesn’t seems so. Wanted to know do you have any link or article from Microsoft where they have accepted it as bug? It would be great if you can share it.

    Like

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