Request conditional data using a workflow API

I’ve created the following API query, but I’d like to hide the fact that I’m looking for something “valid” and was thinking a workflow API might help me do this instead.[{ "key": "websiteid","constraint_type": "equals","value": "1542831846810x186262284968394750"},{"key": "valid","constraint_type": "equals","value": "yes"}]

I’ve created the following workflow API:

I’d like to do a GET on this workflow by submitting a “websiteid” and only having the script return if the script is valid. Is this possible?

I’m doing this so that when a person cancels their subscription they can no longer get data from the database.

Maybe a better question is: How can I use a workflow API to get data from the database?