Validate request parameters in Azure APIM - azure-api-management

Question

I define a full-name API that takes in First Name and Last Name and combine them to return the Full Name:
https://my-org.azure-api.net/my-app/full-name?firstName=John&lastName=Smith
# Returns: John Smith
In Azure APIM, I set both firstName and lastName parameters as "Required" in the API Schema.
In the Inbound policy, I want to validate that both are present in the request. I found the validate-parameters policy which appears to do just that:
<inbound>
<validate-parameters specified-parameter-action="prevent"
unspecified-parameter-action="detect"
errors-variable-name="validationErrors" />
</inbound>
To my surprise, this does absolution nothing! I have to run a manual check on each param (this code is so verbose):
<inbound>
<choose>
<when condition="#( context.Request.OriginalUrl.Query.GetValueOrDefault("firstName") == null )">
<return-response>
<set-status code="400" reason="Bad Request" />
<set-header name="Context-Type" exists-action="override">
<value>text/plain</value>
</set-header>
<set-body>'firstName' is required</set-body>
</return-response>
</when>
<when condition="#( context.Request.OriginalUrl.Query.GetValueOrDefault("lastName") == null )">
<return-response>
<set-status code="400" reason="Bad Request" />
<set-header name="Context-Type" exists-action="override">
<value>text/plain</value>
</set-header>
<set-body>'lastName' is required</set-body>
</return-response>
</when>
<otherwise>
</otherwise>
</choose>
</inbound>
Is there any more convenient way to validate the request against the API's schema in Azure APIM?

Answer 1

We can find the document shows us we need to use api-version which later than 2021-01-01-preview to create the api in APIM, then the policy can work.
So if your api in APIM was created in past, you need to create it again. I checked the create api operation on azure portal, it has been updated to using api-version=2021-01-01-preview shown as below screenshot.
You can also request the api to create it by yourself.