check-name | easiest API to check if there are correct first names | REST library

I need to verify log information(error messages) along with the result set. Here logging can be also understood as report generation in my case.

Should I store the log messages(for any errors) along with result and do the logging after the business logic step

Advantages:

1. This gives me the log information that I can use to verify negative cases during unit testing, versus parsing the log file.
2. Separate out the logging from business logic.
3. I can implement logging as a separate feature, where I can log in different formats based on implementation (HTML, JSON, etc)

Disadvantages

1. This will have code duplication, as I end up with the same loops for logging as for the computation of the result set.
2. During the logging phase the parent will have to fetch the child info. And storing all this info makes it complex and unreadable.

Should I do the logging at the same time as I perform business logic

Advantages

1. Not storing any information and simplifying the solution and effectively passing the context of the parent objects to the child object,
2. Logging when exception occurs.

Disadvantages

1. But not able to separate logging/reporting from business logic.
2. I will not get a log information to verify negative cases for unit-tests. So I will need to parse the log file to verify.

More context below:

I am building this tool for comparison of properties in two resources that can be of type - JSON, properties, VMs, REST API, etc in Python.

The tool reads a metadata json having a structure like follows: