I'm developing a plugin that creates an invoice when a payment is made. But there is not easy way to capture the text with the description of the concept that has buyed.

I think there is 2 posible methods. 

-Include a field in the payments table with the same description that is show in de payment process in paypal)

-add to the service_provider class a method that return that text to a certain itemid ( f.e.  get_concept_text($itemid))

I think is desirable the first option, because that kind of data is transactional and not relational, and must remain inalterable once created.