Pass true to post the message as the authed user, instead of as a bot. Defaults to false. See [authorship](#authorship) below.

A JSON-based array of structured attachments, presented as a URL-encoded string.

A JSON-based array of structured blocks, presented as a URL-encoded string.

Channel, private group, or IM channel to send message to. Can be an encoded ID, or a name. See [below](#channels) for more details.

Emoji to use as the icon for this message. Overrides `icon_url`. Must be used in conjunction with `as_user` set to `false`, otherwise ignored. See [authorship](#authorship) below.

URL to an image to use as the icon for this message. Must be used in conjunction with `as_user` set to false, otherwise ignored. See [authorship](#authorship) below.

Find and link channel names and usernames.

Disable Slack markup parsing by setting to `false`. Enabled by default.

Change how messages are treated. Defaults to `none`. See [below](#formatting).

Used in conjunction with `thread_ts` and indicates whether reply should be made visible to everyone in the channel or conversation. Defaults to `false`.

How this field works and whether it is required depends on other fields you use in your API call. [See below](#text_usage) for more detail.

Provide another message's `ts` value to make this message a reply. Avoid using a reply's `ts` value; use its parent instead.

Pass true to enable unfurling of primarily text-based content.

Pass false to disable unfurling of media content.

Set your bot's user name. Must be used in conjunction with `as_user` set to false, otherwise ignored. See [authorship](#authorship) below.