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Custom Connector: Header "content-type" not sent to service

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Posted on by Frank37

I would like to connect to an RestAPI-Service, which needs the header information:

"content-type": "application/x-www-form-urlencoded"

but have problems using it as well in Flow as in PowerApps

Error code/status is 415: Unsupported Media Type Content type '' not supported

To reproduce the problem, I tested it with the Postman Echo Server and two header keys: "content-type" and "MyContentType":

In Postman both Key/Value are echoed:

I generate a custom connector with these two header parameters

and the default response 200:

The custom connector test shows no error and no problem: both keys are in the response:

Problem:

If I use it in a Flow "content-type" is missing, only "MyContentType" is accessable:

I've testet the runtime server input: both parameters are transfered to the azure platform

{
 "method":"post",
 "headers":{
 "Content-Type":"application/x-www-form-urlencoded",
 "MyContentType":"application/x-www-form-urlencoded"
 },
 "path":"/post",
 "host":
 {
 "api":
 {
 "runtimeUrl":"https://europe-002.azure-apim.net/apim/flowposttest-5f7e5f68ae5b1cf2d2-5f79e327c051ec9794"
 },
 "connection":
 {"name":"/providers/Microsoft.PowerApps/apis/shared_flowposttest-5f7e5f68ae5b1cf2d2-5f79e327c051ec9794/connections/e38ffb06-9eb2-451d-a51a-5509-8628e957"
 }
 },
 "authentication":
 {
 "scheme":"Key",
 "parameter":"*sanitized*",
 "type":"Raw"
 }
}

Why is the Azure Server deleting the "content-type" parameter?

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Using connectors

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v-alzhan-msft Microsoft Employee on at

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Hi @Frank37 ,

Have you created the "content-type" for the output of the custom connector?

Could you please take a try to add a Compose action under custom connector, and check if you could add am expression or a dynamic content for the "content-type"?

Best regards,

Alice

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

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Frank37 61 on at

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Hi Alice,

yes, "content-type" is defined for the output of the custom connector, but only to show, that the azure platform is deleting the HTTP-header-parameter "content-type"

IT's not possible to add a Compose Action, which changes the HTTP-header of the custom connector action. You can only change the url parameters.

Here is a sample Swagger-File for a custom connector (OpenAPI)

If using the custom connector test funktion, the "content-type" header-parameter is sent to the server (and echoed in the reply).
If using this connector in flow (or PowerApps), the azure platform deletes the "content-type" header-parameter (why?) and in the echo reply the parameter is missing

{ "swagger": "2.0", "info": { "description": "Postman Echo Server", "version": "0.1", "title": "MyTest2" }, "host": "postman-echo.com", "basePath": "/", "schemes": [ "https" ], "consumes": [], "produces": [], "paths": { "/post": { "post": { "consumes": [ "application/x-www-form-urlencoded" ], "produces": [ "application/json" ], "parameters": [ { "name": "Content-Type", "in": "header", "required": true, "type": "string", "default": "application/x-www-form-urlencoded", "x-ms-visibility": "internal" }, { "name": "MyContentType", "in": "header", "required": true, "type": "string", "default": "application/x-www-form-urlencoded", "x-ms-visibility": "internal" } ], "responses": { "200": { "description": "default", "schema": { "type": "object", "properties": { "url": { "type": "string", "description": "url" }, "headers": { "type": "string", "description": "MyContentType" }, "Content-Type": { "type": "string", "description": "Content-Type" } } } } }, "summary": "Echo Server Test", "description": "Echo Server Test", "operationId": "EchoServerTest" } } }, "parameters": {}, "responses": {}, "securityDefinitions": {}, "security": [], "tags": [] }

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Verified answer

Frank37 61 on at

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Here is the solution from GonzaloR (worked for me 👍)

https://powerusers.microsoft.com/t5/General-Power-Automate/Custom-connector-action-with-x-www-form-u...

Click "New Policy"
Name your policy
Select "Set HTTP header"
Select the Operations (Actions) that require this header
Header name: "content-type"
Header Value: "application/x-www-form-urlencoded"
Action if header exists: "override"
Run policy on: "Request"

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derb 30 on at

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Thank you sooo much! You solved my problem with my custom connector that I could not figure out! Virtual hugs and joy! I have been trying to modify the URL by changing the sample input for about an hour without success... This worked like a charm!

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jackp514 47 on at

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To any one still struggling with this issue, none of these solutions fixed the error for me. The only thing that worked was putting SOMETHING in the "body"

If you put "{ }" in the body it seems to work now.

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