Retrieves JSON Schema definitions for port-in fields, keyed by port-in type. Use these schemas for client-side validation of port-in form data before submission.

Each key in the response corresponds to a port-in type (e.g., "personal", "business"), and the value is a standard JSON Schema object that can be used with any JSON Schema validator.

A type whose market declares transfer dates also carries $defs.executionDate: check the port-in's executionDate against it. Its dates hold until the executionDate.validUntil the fields endpoint returns; fetch the schema again after it. Nothing in the schema's properties refers to it, so the schema validates fields alone.