Every Discord platformSpecificData field and the attachment requirements.

Media requirements

A message takes up to 10 attachments of 25 MB each.

Media URLs must be publicly reachable HTTPS URLs; upload files through the media endpoint to get one. A poll cannot carry attachments.

Platform fields

All fields go in platformSpecificData on the Discord entry. channelId is required.

Field	Type	Default	Description
`channelId`	string		Snowflake id of the target channel. Required.
`embeds`	Array<object>		Up to 10 Discord embed objects, 6,000 characters combined. See Embeds.
`poll`	object		Native poll (question, answers, duration). Cannot be combined with media. See Polls.
`crosspost`	boolean	`false`	Publish to every follower of an announcement channel. No-op on text channels.
`forumThreadName`	string		Thread title for a forum starter message. Required on forum channels.
`forumAppliedTags`	Array<string>		Tag snowflake ids for a forum post, at most 5.
`threadFromMessage`	{name, autoArchiveDuration?, rateLimitPerUser?}		Open a thread under the published message. See Threads.
`tts`	boolean	`false`	Text-to-speech message: Discord reads it aloud in the channel.
`webhookUsername`	string	account default	Display name for this post only, 1 to 80 characters.
`webhookAvatarUrl`	string	account default	Avatar URL for this post only.

A message takes up to 10 attachments of 25 MB each.

Media URLs must be publicly reachable HTTPS URLs; upload files through the media endpoint to get one. A poll cannot carry attachments.

All fields go in platformSpecificData on the Discord entry. channelId is required.

Field	Type	Default	Description
`channelId`	string		Snowflake id of the target channel. Required.
`embeds`	Array<object>		Up to 10 Discord embed objects, 6,000 characters combined. See Embeds.
`poll`	object		Native poll (question, answers, duration). Cannot be combined with media. See Polls.
`crosspost`	boolean	`false`	Publish to every follower of an announcement channel. No-op on text channels.
`forumThreadName`	string		Thread title for a forum starter message. Required on forum channels.
`forumAppliedTags`	Array<string>		Tag snowflake ids for a forum post, at most 5.
`threadFromMessage`	{name, autoArchiveDuration?, rateLimitPerUser?}		Open a thread under the published message. See Threads.
`tts`	boolean	`false`	Text-to-speech message: Discord reads it aloud in the channel.
`webhookUsername`	string	account default	Display name for this post only, 1 to 80 characters.
`webhookAvatarUrl`	string	account default	Avatar URL for this post only.