How do 'JSON structure validation errors' manifest when integrating with GST APIs, and what are typical API responses?

When integrating with GST APIs, these errors typically result in an HTTP `400 Bad Request` status code. The API response payload will usually contain a detailed error message, often with an `error_code` and a human-readable `message` field. The `message` frequently specifies the exact field path (e.g., `$.b2b[0].inv[0].txval`) and the nature of the error (e.g., 'Field 'txval' is required', 'Invalid data type for 'inum'', 'Date format mismatch').