Content type
discord_message — caption optional. Up to 10 files. GIFs are kept as GIF.
Meta
There is no public REST search for Discord members or roles — construct mention tokens yourself.
Platforms
Discord
Channel messages with media, mentions, and embeds. channel_id is required to publish.
A channel is required to publish. Pick it when you compose the post — list channels if you are on the API. How the browser flow works: Connect accounts.