descriptors are documented here: https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md
Here's an example extended public key with derivation path to 'external_index/address_index' ( /0/* ) and with 'range' argument.
(commonly used path for deriving receiving addresses from an xpub):
importdescriptors "[{\"desc\": \"wpkh(tpubDC8SbfxbQot4BA2kg476RyWA5EM5yawYj9ZUMbAtDeBEBgPNVTyAYRKDCLJQcbUP1yBus4Z9BUMSZANmaNGruFYnfPXwXBDLrPyU8vM7QWy/0/*)#wg24ts7y\",\"timestamp\": \"now\",\"range\": [0,100]}]"