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Cusom Connectors: Policy templates: expressions not working



In my Custom Connector I need an expression in the policy




I have a query parameter named "content-format"


I defined a policy

- template: Set HTTP-Header

- operation: (my action selected)

- header name: content-type

- header value: @queryParameters(‘content-format’)

- action if header exists: overide

- run policy on: request


If I test my action, the answer from the azure platform is:


  "error": {
    "code": 500,
    "message": "Invalid parameters template. No property names specified in @headers or @queryParameters or @connectionParameters expression",
    "source": "",
    "path": "choose[4]\\when[1]",
    "clientRequestId": "cecfe20d-ddfa-4384-8624-f1aa-63c8c81f"


Where ist my error?



Community Support
Community Support

Re: Cusom Connectors: Policy templates: expressions not working

Hi @Frank37 ,

Please check whether your api has access to the data source.

You could try to switch off authorization and do firewall rule and On-Premises gateway connection for security.

Here's a similar issue for your reference:

What's more, here's a doc about how to use this template that may help you for your reference:



Best regards,

Community Support Team _ Phoebe Liu
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Frequent Visitor

Re: Cusom Connectors: Policy templates: expressions not working

Hi Yutliu, the API access to the data source is OK: If I do not use the policy, the action is sent successfully to the server. This error only occurs if I enable the policy for this action (but I need the policy to make the action work correct) Frank

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