Resolved this by using dbutils within the notebook being called from the API.

# databricks notebook function
 
data = dbutils.widgets.get('data') # pulls base_parameters from API call
 
def add_test(i):
    result = i + ' COMPLETE'
    return result
 
dbutils.notebook.exit(str(add_test(data))

Output from API call:

COMPLETED

{'result': 'test COMPLETE', 'truncated': False}