CAP

The CAP command is used for capability negotiation between clients and servers.
Capability Negotiation
Usage: CAP <subcommand> [<parameters>]
<subcommand> The capability subcommand (e.g., LS, LIST, REQ, END, ACK, NAK, CLEAR).
<parameters> (Optional) Parameters specific to the subcommand.

(See section Client Capability Negotiation of IRCv3)