The ntp server command, e.g., ntp server "172.20.0.188" "nts" 6666, should detect an error when a non-existent key ID (e.g., 6666) is configured via CLI. However, the current ui_ntp_server() function does not check for this and proceeds with the setup.
To address this, I added a condition at the beginning of the function to validate the key ID. It reads /ca/conf/chrony.keys, which stores authentication keys for NTP servers, parses the file, and extracts the key IDs. If the user-provided key ID matches one from the file, the function continues execution. Otherwise, it displays an error message:

Unknown Authentication Key ID: 6666

and returns 1.

AN(config)#show ntp keys          

key ID     MD5 String                      

1          hello                           
AN(config)#ntp server "172.20.0.188" nts 6666

Unknown Authentication Key ID: 6666.

AN(config)#ntp server "172.20.0.188" nts 1   
AN(config)#