Have a schema that you want to reuse in multiple places? Create a Model. Models represent schema objects that allow the definition of input and output data types. Should be used to reduce duplication. Models can be reused with other models, in traits or with endpoints. Use $ref to refer an existing model.
Traits will help you to define generic request and response patterns like query parameters, headers, response types (200, 404) ect and their respective response schemas. You can reuse them with endpoints.