The Slack MCP that turns channel activity into workflows
Connect a Slack bot token once and messages, reactions, channels, and history become steps on an automation canvas. Two webhook triggers start workflows the moment someone posts or reacts.
What the Slack MCP connector does
The Slack connector for Mattering Automations is a focused set of 10 nodes over the Slack Web API: send and update messages, add an emoji reaction, create a channel, invite users to it, set its topic, read channel history, and look up a user. Two trigger nodes fire from Slack events, one when a message is posted in a channel and one when a reaction is added to a message.
Each node is a block on the Automations canvas, and every node speaks MCP, the open protocol for connecting AI assistants to tools. Claude, ChatGPT, and any MCP-capable assistant can use them, and they also power Matter, the AI assistant built into the platform. Describe the Slack workflow you want in plain language and it gets built on the canvas in front of you.
This is deliberately a working surface rather than a mirror of the whole Slack API. What it covers, it covers honestly: the nodes call chat.postMessage, chat.update, reactions.add, conversations.create, conversations.invite, conversations.setTopic, conversations.history, and users.info. Other Slack Web API methods stay reachable through the generic HTTP Request node using the same Slack bot token credential.
One connection, three surfaces
- Visual automations. Drag Slack nodes onto the canvas and wire them to triggers, conditions, and other apps.
- AI agents, yours or ours. These nodes speak MCP, the open protocol, so Claude, ChatGPT, and any MCP-capable assistant can use them, and Matter, the agent built into the platform, uses them natively.
- The whole platform. Combine with native tasks, projects, and other connectors, no middleware in between.
Every Slack node, ready to drop on the canvas
10 nodes, generated from the connector itself so this list always matches what ships. Expand a category to browse.
Trigger nodes (start workflows from events) 2
Slack Message
Fires when a message is posted in a Slack channel
Slack Reaction
Fires when a reaction is added to a message
Read and query nodes 2
Slack Channel History
Read message history from a Slack channel
Slack User Info
Get information about a Slack user
Action nodes 6
Add Slack Reaction
Add an emoji reaction to a message
Create Slack Channel
Create a new Slack channel
Invite to Slack Channel
Invite users to a Slack channel
Send Slack Message
Send a message to a Slack channel or user
Set Slack Topic
Set the topic of a Slack channel
Update Slack Message
Update an existing Slack message
Connecting Slack takes one credential
Create or open a Slack app at api.slack.com/apps, add the bot token scopes the methods you plan to call require, install the app to your workspace, and copy the Bot User OAuth Token from the OAuth and Permissions page. It starts with xoxb-. User tokens starting with xoxp- are also accepted. Mattering sends whichever token you paste as a bearer token.
In your Slack app's OAuth and Permissions page, add the bot token scopes the Slack methods you plan to call require, then install the app to your workspace.
Copy the Bot User OAuth Token.
In Mattering Automations, open Connectors, choose Slack, and create a credential holding the token.
Run Test Connection: Mattering calls Slack's auth test endpoint and reports which workspace it authenticated as.
All 10 Slack nodes appear in the canvas palette. Trigger nodes show a webhook URL to paste into your Slack app's Event Subscriptions.
Common uses for the Slack MCP
Alerts that land where people already are
Any workflow step can end in a Slack message: a failed run, a new lead, a signed contract, a daily summary. One node posts it to the channel or person who needs it, with the values from earlier steps filled in.
A reaction as a triage signal
Someone adds an agreed reaction to a message and the reaction trigger starts a workflow: read the channel context, create an assigned task in Mattering Productivity, and reply in the thread with the link.
Channel setup for every new project or deal
When work starts, create the channel, invite the people on it, and set the topic in three steps, so every project gets the same structure without anyone doing it by hand.
AI answers on new messages
The message trigger hands a new post to an AI step that drafts a reply, checks it against your knowledge base, and posts the answer back into the thread.
Status messages that update in place
Post one message when a long job starts, then use the message timestamp it returns to update that same message as the run progresses, instead of flooding the channel with new posts.
Digests built from channel history
On a schedule, read a channel's recent history, have an AI step summarize decisions and open questions, and post the digest back to the channel or store it as a task.
Example: A reaction on a Slack message becomes a tracked task
Built on the Automations canvas in a few minutes, or described in plain language to Matter and built for you.
Trigger: Slack Reaction fires when someone adds a reaction to a message.
A condition step checks the reaction name so only your agreed triage reaction continues.
Slack: Slack Channel History reads recent messages from the channel the reaction landed in, giving the workflow the message text.
Slack: Slack User Info resolves who reacted, so the task records a real name rather than a user id.
Mattering Productivity: a task is created with the message text, the reporter, and a due date.
Slack: Send Slack Message replies in the thread with the task link, so the channel sees it was picked up.
Slack MCP questions, answered
What Slack actions are supported?
Ten nodes. Six actions: Send Slack Message, Update Slack Message, Add Slack Reaction, Create Slack Channel, Invite to Slack Channel, and Set Slack Topic. Two queries: Slack Channel History and Slack User Info. Two triggers: Slack Message and Slack Reaction. That is the whole set. It is a focused working surface, not an exhaustive wrapper around the Slack API, and the page will change only when the node list does.
Does this work with Claude, ChatGPT, or other AI assistants?
Yes. Mattering exposes these nodes over MCP, an open protocol for connecting AI assistants to tools, so any MCP-capable assistant, including Claude and ChatGPT, can connect to your workspace and work with Slack through them. Matter, the assistant built into the platform, uses the same nodes natively.
What credential does the connector use?
A Slack bot user OAuth token, the one starting with xoxb- from your Slack app's OAuth and Permissions page. It is sent as a bearer token and stored encrypted in Google Secret Manager, and it never appears in workflow logs. User tokens starting with xoxp- are also accepted if that is the identity you want automations to act as.
Which Slack scopes does my app need?
It depends on which nodes you use, and Slack is the source of truth: every method page on api.slack.com/methods lists the scopes that method requires. The connector calls chat.postMessage, chat.update, reactions.add, conversations.create, conversations.invite, conversations.setTopic, conversations.history, and users.info, so grant the bot token scopes those methods ask for and skip the rest. Adding a scope later means reinstalling the app and updating the credential with the new token.
Can a Slack message or reaction start a workflow?
Yes. Both triggers run on Slack's Events API rather than polling. Each connection mints a webhook URL that you paste into your Slack app's Event Subscriptions as the request URL, then subscribe to the message and reaction events you want. When an event arrives, every active automation containing that trigger node runs with the event payload. Messages posted by bots are ignored, so a workflow that posts to Slack will not retrigger itself.
What is not supported?
File uploads, message search, scheduled messages, workspace and user administration, and Block Kit layouts are not exposed as nodes. Send Slack Message posts text, with an optional thread timestamp for replying in a thread. Anything outside the ten nodes is reachable through the generic HTTP Request node using the same Slack bot token credential, which is the honest answer rather than implying broader node coverage.
What are Slack's rate limits?
Slack applies per-method rate limits and documents them alongside each method in its API documentation, which is the source of truth for current numbers. When Slack throttles a call, the connector returns the error on the node output so the workflow can wait and retry rather than failing silently.
How is this different from Zapier's Slack integration?
Zapier connects Slack to other apps. Mattering combines Slack with native tasks, projects, databases, and AI agents on one canvas, so a reaction can become an assigned task with a due date, an agent can draft the reply, and the whole flow is one thing you can see and edit. The node set here is smaller and stated plainly rather than padded.
Put Slack to work inside your workspace
Connect once, then use every node in visual automations and AI agent workflows across the Mattering platform.
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