Calling Palantir Foundry Ontology Action using API from Code Repo/Workbook

I'm trying to call a Palantir Foundry Ontology Action (Function backed) via API which I got from Browser's Network Tab when executing the action.

Path: /actions/api/actions

Sample Payload (masked):

{"actionTypeRid": "ri.actions.main.action-type.aaaaaaa1","parameters": {"ri.actions.main.parameter.xparam1": {"type": "string","string": "value1"        },"ri.actions.main.parameter.xparam2": {"type": "string","string": "value2",        }    }}

I'm getting the below error:

    requests.exceptions.HTTPError: 400 Client Error: Bad Request for url

How can I resolve this? Is there another way to call the Action or the backing OntologyEditFunction?