I am using the rest interface because I have my application in go and there is no standard lib for it.
Here is the curl
curl --location '
https://googleads.googleapis.com/v17/customers/4926841893/campaigns:mutate' \
--header 'developer-token: hN6dsqjNmj3tWdITcPd_Qg' \
--header 'login-customer-id:
3263459376' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer ya29.a0AXooCgv756eKpN5h9TWccVdZyq6GUs3YQlA2cFipbDaF41dzXhxZVq40lzFZd3DyMZCv1a7x0hZZnBUah85MkWOcFQ9hELxZw01dkyAqyCIxKORk7vLL1C_A_zbiTANsXSjOV1Gr0W-hRhL6gbq7pZPpPADhnDiLE1jBaCgYKAcASARMSFQHGX2MikC5FoOFEJUQdN6Ayq8jmIw0171' \
--data '{
  "operations": [
    {
      "create": {
        "name": "A video campaign",
        "status": "PAUSED",
        "campaignBudget": "customers/4926841893/campaignBudgets/13757766883",
        "advertisingChannelType": "VIDEO",
        "targetCpa": {
          "targetCpaMicros": 5000000
        }
      }
    }
  ]
}
'
and the response
{
  "error": {
    "code": 400,
    "message": "Request contains an invalid argument.",
    "status": "INVALID_ARGUMENT",
    "details": [
      {
        "@type": "
type.googleapis.com/google.ads.googleads.v17.errors.GoogleAdsFailure",
        "errors": [
          {
            "errorCode": {
              "contextError": "OPERATION_NOT_PERMITTED_FOR_CONTEXT"
            },
            "message": "The operation is not allowed for the given context.",
            "location": {
              "fieldPathElements": [
                {
                  "fieldName": "operations",
                  "index": 0
                },
                {
                  "fieldName": "create"
                },
                {
                  "fieldName": "target_cpa"
                }
              ]
            }
          },
          {
            "errorCode": {
              "mutateError": "MUTATE_NOT_ALLOWED"
            },
            "message": "Mutates are not allowed for the requested resource.",
            "trigger": {
              "stringValue": "VIDEO"
            },
            "location": {
              "fieldPathElements": [
                {
                  "fieldName": "operations",
                  "index": 0
                }
              ]
            }
          }
        ],
        "requestId": "QudlAS83vMKB-XjTYG7TUQ"
      }
    ]
  }
}
Thanks for your help