HTTP status code 429 indicates that too many requests have been sent in a given amount of time, which is a sign of rate limiting. Rate limiting is used by APIs to control the amount of incoming requests to prevent abuse or overloading the server. In this case, the Cisco Prime API is limiting the number of requests the network engineer can make in a certain time period, resulting in only a subset of devices being returned and some requests being rejected with a 429 status code.