In the first article of this series , we introduced Okyline — a JSON validation language where your examples become your schemas. We walked through an e-commerce order, from a bare JSON payload to a fully constrained contract with computed business rules. This time, we're going deeper into one specific area: conditional logic . The rules that say "this field is required when that field has this value" or "these fields change depending on the variant". The kind of rules every real-world API has, and the kind that turn JSON Schema into something nobody wants to read. We'll use a hotel reservation as a running example and build the contract step by step. The starting point Here's a simplified hotel reservation payload.…