Slack Action

Posts and manages Slack from a flow. Sixteen operations across messages, channels, reactions, users and files — including the two that people usually reach for a bot to get: an ephemeral message only one person sees, and a message scheduled for later.

Setup

Pick a Slack credential — an OAuth connection or an incoming webhook. A webhook can post to the channel it was created for and nothing else, so choosing it narrows the operation list accordingly.

Mode — action or AI toolkit

The Mode selector decides who drives the node. In Action mode you pick one operation and fill its fields, and the node does that every time it runs. In AI toolkit mode the operations become tools an AI Node can call, and the model chooses which one and with what arguments.

ℹToolkit mode is opt-in per node, and it is what makes this node show up in an AI Node's tool picker. A node left in Action mode is invisible to agents.

Operations

The Operation dropdown decides what the node does and which fields appear under it. These are the exact values the API validates against:

Value	In the dropdown	What it does
sendMessage	Send message	Post a message to a channel, group, or DM.
updateMessage	Update message	Edit a message the bot posted earlier.
deleteMessage	Delete message	Delete a message the bot posted earlier.
sendEphemeral	Send ephemeral	Post a message visible only to a single user (the rest of the channel does not see it).
scheduleMessage	Schedule message	Schedule a message to be posted at a future time.
getMessage	Get message	Fetch a single message by its timestamp.
listChannels	List channels	List public + private channels the bot can see in the workspace.
getChannelHistory	Get channel history	Read recent messages from a channel.
getThreadReplies	Get thread replies	Fetch replies to a thread.
createChannel	Create channel	Create a new public or private channel.
inviteToChannel	Invite to channel	Invite one or more users to a channel.
addReaction	Add reaction	Add an emoji reaction to a message.
removeReaction	Remove reaction	Remove an emoji reaction from a message.
listUsers	List users	List human members of the workspace (excludes deleted users + bots by default).
getUserInfo	Get user info	Fetch a user profile (name, email, timezone, status).
uploadFile	Upload file	Upload a file (PDF, image, anything) and optionally share it in a channel.
updateProfile	Update profile	Change a member's names, title, phone or status. Empty user = the account that connected.
createUser	Create user	Create a member of the workspace.
updateUser	Update user	Change a member's username, names, email or title, or reactivate them.
deleteUser	Delete user	Deactivate a member. Slack keeps the account; Update user can reactivate it.

People are picked, not typed. Invite to channel lists the workspace's members by name — bots and deactivated accounts left out — and takes several at once. To take them from the flow, choose Type IDs or a template under the list.

Gotchas

Posting works anywhere public; reading needs the bot inside. The bot can post to any public channel without joining. Reading a message, the history or a thread, reacting, and receiving trigger events need it in the channel: use Add bot next to the channel picker (public channels) or /invite @HostWebhook (private ones). Otherwise Slack answers not_in_channel.
Create channel, Invite and user emails need newer permissions. HostWebhook asks for channels:manage, groups:write and users:read.email since 2026-10-03. A Slack credential connected before that gets missing_scope on those operations (and empty emails) until you reconnect it in Settings → Credentials.
Upload file takes a file of this run (its id, shown to an AI agent under "Files in this event", or {{payload._file.downloadUrl}}), a public URL, or inline base64 — up to 50 MB. A file's link is signed again when the node runs, so it still works after a Delay or an approval.
Block Kit: paste the whole Block Kit Builder payload or just its blocks array. Templates inside blocks — including {{$resumeUrl("…")}} in a button — are filled in when the node runs.
Post at accepts a template, e.g. one hour from now: {{$timestamp | divide(1000) | add(3600) | round}} (Unix seconds).
List channels / List users page through Slack up to limit (200 by default, 1,000 at most) and say hasMore when there are more.
Errors keep their meaning. A missing permission, a channel or message that does not exist, or a bad field fails with a 4xx and is not retried; Slack's rate limit (429) and outages (503) are.
Managing users (Create, Update, Delete user and Update profile) needs a Slack credential connected with Manage users turned on, by a Slack Owner or Admin. Create, Update and Delete user need Slack Business+ or Enterprise; Delete user deactivates (Owners can't be deactivated).
Editing and deleting only work on the bot's own messages.
ts is the message id. Slack identifies messages by timestamp, so keep the ts a send returns if you plan to edit, delete or thread onto it.
Thread replies use threadTs, the parent's ts — not the reply's.
Blocks beat text. Passing blocks gives you the layout; text is still worth filling because it is what notifications show.