Slack: posting rules and settings

What a Slack channel accepts in Postemi: media, limits, required fields, and the fields of the settings object for the API.

Basics

Post types

The same channel accepts more than one kind of post, and each kind has different requirements. The table shows what you need for each.

Rules

• The destination channel is required, and it expects an ID. You fetch the list of channels with the channel's tool call.

Settings fields

These fields go into the post's settings object, alongside the __type field. In the UI, you fill in the same ones in the channel's settings section.

Examples

Each example is one item in the POST /public/v1/posts request's posts array. The envelope around it is always this:

{
  "type": "schedule",
  "date": "2026-09-15T09:00:00.000Z",
  "shortLink": false,
  "posts": [ /* the item below */ ]
}

{
  "integration": { "id": "<slack-channel>" },
  "value": [{ "content": "<p>Weekly summary.</p>", "image": [] }],
  "settings": { "__type": "slack", "channel": "<channel-id>" }
}

The channel ID comes from the channel list, and the path values for images and videos from media upload. The exact schema for the connected account comes from the settings schema endpoint. From the command line, the same thing is the --settings flag. See the CLI examples.