Get metadata for batch of files

That error indicates that you're hitting a rate limit, so you'd need to catch that error and have your app wait before trying again. The Dropbox API has a rate limiting system in order to protect against high rates of calls. Note that not all 429s and 503s indicate explicit rate limiting, but in any case that you get a 429 or 503 the best practice is to retry the request, respecting the Retry-After header if given in the response, or using an exponential back-off, if not.