Facebook Lead Ad (leads forms) campaign via API - Objective error for version 18

Question

I am trying to create a new Lead Ad campaign following the documentation https://developers.facebook.com/docs/marketing-api/guides/lead-ads/create

The problem is I am getting this error - "(#100) Objective LEAD_GENERATION is invalid. Use one of: OUTCOME_LEADS, OUTCOME_SALES, OUTCOME_ENGAGEMENT, OUTCOME_AWARENESS, OUTCOME_TRAFFIC, OUTCOME_APP_PROMOTION."

I am only trying to create a campaign. I am not in the "Ad Set" step yet.

What I have from the documentation is a POST request - https://graph.facebook.com/v18.0/act_AD_ACCOUNT_ID/campaigns

{
  "buying_type": "AUCTION",
  "name": "Lead_test_campaign",
  "objective": "LEAD_GENERATION",
  "special_ad_categories": "[\n  \"NONE\"\n]",
  "status": "PAUSED"
}

Searching for a solution, I found this post here in Stack Overflow where the solution is to add destination_type": "ON_AD" to the ad set params, but I am not the Ad Set level creation yet.

How can I create the campaign without getting this error and not creating the Ad Set simultaneously?

Thanks!