Reports

The body of your Send an HTTP request to SharePoint action is just a little bit off. Here JSON body package I used to successfully create a lookup column in a SharePoint document library using Power Automate:

{
  'parameters': {
    '__metadata': {
      'type': 'SP.FieldCreationInformation'
    },
    'FieldTypeKind': 7,
    'Title': '<your column title>',
    'LookupListId': '<your lookup list ID>',
    'LookupFieldName': '<your lookup column name>'
  }
}

You didn't mention what endpoint you were using, but for this example I used _api/web/lists/getbytitle('<your document library title')/fields/addfield

Also, be sure your action's method is set to POST and you have the following headers:

accept: application/json;odata=verbose
content-type: application/json;odata=verbose

Please let me know if this works!

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