I need to update a column for each item in my SharePoint list, with information from a another SharePoint list in another subsite. I’m using Sharepoint Designer 2013 and have set up a SharePoint 2013 item workflow, that runs each time an item is created, and uses an API call to the SharePoint REST API for the other subsite’s list.

However, I get the following access denied error:

{"odata.error":     {"code":"-2147024891, System.UnauthorizedAccessException",     "message":         {"lang":"en-US",         "value":"Access denied. You do not have permission to perform this action or access this resource."}     } } 

I personally have permissions on the subsite, so I can modify whatever permissions are required, but I’m not sure what to change- what permissions are actually being checked here? Is there something like a workflow system account that I need to give read access to the other subsite?