An FTO analysis is needed when a product enters a new market, raises investment, is licensed, or moves into a competitive area with active patenting. For IT this matters especially: the risk may be hidden not in the interface but in the method of processing data.
A useful FTO report is not a list of the patents found. It should show which features of the product potentially read on the independent claims, where there is room to design around, and which changes to the architecture reduce the risk.