I was getting the above error while trying to deploy Bicep templates for an Azure API Management API.

Specifically, I was trying to use the validate-content policy to validate the JSON schema of the request body.

I had this to define my API’s operation (i.e. endpoint):

resource CreateRatingUnitOperation 'Microsoft.ApiManagement/service/apis/operations@2023-03-01-preview' = {
  parent: Api
  name: 'createratingunit'
  properties: {
    displayName: 'Create Rating Unit'
    method: 'POST'
    urlTemplate: '/rating-unit'
    description: 'Create a rating unit changed notification'
    request: {
      representations: [
        {
           contentType: 'application/json' 
           schemaId: 'property-definition' // this is needed for the validate-content policy to work
        }
      ]
    }
    responses: [
      {
        description: 'success'
        statusCode: 201
      }
    ]
  }
}

But actually, the schemaId is not needed to be defined here. Removing the schemaId (but leaving contentType: ‘application/json’) fixes the problem.