Slack

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Documentation

Guide

Your entire Slack workspace, accessible through AI.

A Model Context Protocol (MCP) server that exposes Slack's API for messaging, channel management, user discovery, and workspace administration.

Overview

The Slack MCP Server provides comprehensive access to your Slack workspace:

Send, read, edit, delete, and search messages across channels and threads
Manage channels — create, archive, invite users, and browse the workspace roster
Search files, find users, extract threads, and inspect workspace metadata

Perfect for:

AI assistants that need to send or read Slack messages on your behalf
Automating channel management, notifications, and team coordination
Building tools that integrate Slack with other services and workflows

Tools

Messaging

Posts a message to a Slack channel or direct message, with optional rich formatting via Block Kit.

Inputs:

- `channel` (string, required) — Channel ID or name (e.g., #general or C123ABC456)
- `text` (string, optional) — Plain text message (up to 4000 characters)
- `blocks` (list, optional) — Slack Block Kit JSON for rich formatting
- `thread_ts` (string, optional) — Parent message timestamp to reply in a thread
- `reply_broadcast` (bool, optional) — Also broadcast the reply to the channel (default: false)

output:

{
  "ok": true,
  "channel": "C123ABC456",
  "ts": "1234567890.123456",
  "message": { "text": "Hello!", "user": "U123" }
}

Retrieves message history from a channel with optional timestamp range filtering.

Inputs:

- `channel` (string, required) — Channel ID or name
- `limit` (int, optional) — Number of messages to return (1–100, default: 20)
- `oldest` (string, optional) — Oldest timestamp cutoff (Unix timestamp)
- `latest` (string, optional) — Latest timestamp cutoff (Unix timestamp)

output:

{
  "ok": true,
  "messages"

Edits the text or blocks of an existing message in a channel.

Inputs:

- `channel` (string, required) — Channel ID
- `ts` (string, required) — Timestamp of the message to update
- `text` (string, optional) — New text content
- `blocks` (list, optional) — New Block Kit JSON

output:

{
  "ok": true,
  "channel": "C123ABC456",
  "ts": "1234567890.123456",

Permanently deletes a message from a channel.

Inputs:

- `channel` (string, required) — Channel ID
- `ts` (string, required) — Timestamp of the message to delete

output:

{
  "ok": true,
  "channel": "C123ABC456",
  "ts": "1234567890.123456"
}

Searches all messages across the workspace using a query string, with sorting options.

Inputs:

- `query` (string, required) — Search query string
- `sort` (string, optional) — Sort by: score or timestamp (default: score)
- `sort_dir` (string, optional) — Sort direction: asc or desc (default: desc)
- `count` (int, optional) — Number of results to return (default: 20)

output:

{
  "ok": true,
  "messages": {
    "total":

Posts a reply to a specific thread, with the option to broadcast it to the channel.

Inputs:

- `channel` (string, required) — Channel ID
- `thread_ts` (string, required) — Timestamp of the parent message to reply to
- `text` (string, optional) — Reply text content
- `blocks` (list, optional) — Block Kit JSON for rich formatting
- `broadcast` (bool, optional) — Broadcast the reply to the channel (default: false)

output:

{
  "ok": true,
  "ts":

Channel Management

Returns a paginated list of channels with optional type and archived filtering.

Inputs:

- `exclude_archived` (bool, optional) — Skip archived channels (default: true)
- `limit` (int, optional) — Channels per page (1–100, default: 20)
- `cursor` (string, optional) — Pagination cursor from response_metadata.next_cursor
- `types` (string, optional) — Comma-separated channel types: public_channel, private_channel, mpim, im (default: public_channel)
- `team_id` (string, optional) — Team ID for org-wide apps only

output:

Creates a new public or private Slack channel.

Inputs:

- `name` (string, required) — Channel name (lowercase, no spaces or special characters)
- `is_private` (bool, optional) — Create as a private channel (default: false)
- `description` (string, optional) — Channel description

output:

{
  "ok": true,
  "channel": { "id": "C456", "name":

Returns metadata for a specific channel including member count and settings.

Inputs:

- `channel` (string, required) — Channel ID

output:

{
  "ok": true,
  "channel": {
    "id": "C123",
    "name": "general",
    "num_members": 42,
    "topic": {

Invites one or more users to an existing channel.

Inputs:

- `channel` (string, required) — Channel ID
- `users` (list, required) — List of user IDs to invite

output:

{
  "ok": true,
  "channel": { "id": "C123", "name": "general", "members": ["U123", "U456"

Search & Discovery

Searches files in the workspace by query and optional type filter.

Inputs:

- `query` (string, optional) — Search query string
- `sort` (string, optional) — Sort by: score or timestamp (default: score)
- `sort_dir` (string, optional) — Sort direction: asc or desc (default: desc)
- `count` (int, optional) — Number of results to return (default: 20)
- `types` (string, optional) — File type filter (e.g., images, pdfs, docs)

output:

{
  "ok": true,
  "files"

Fetches all channels in the workspace (with automatic pagination) and returns them with metadata.

Inputs:

- `include_archived` (bool, optional) — Include archived channels (default: false)

output:

{
  "ok": true,
  "channels": [{ "id": "C123", "name": "general", "num_members": 50 },

Looks up a user by their Slack ID, display name, real name, or email address.

Inputs:

- `query` (string, required) — User name, email address, or Slack user ID (e.g., U123ABC)

output:

{
  "ok": true,
  "matches": [{ "id": "U123", "name": "jane", "real_name": "Jane Doe",

Retrieves thread metadata (reply count, latest reply, original message) from recent messages in a channel.

Inputs:

- `channel` (string, required) — Channel ID
- `limit` (int, optional) — Number of messages to scan for threads (default: 10)

output:

{
  "ok": true,
  "threads": [
    { "ts": "...", "user": "U123",

Workspace & Users

Returns a paginated list of all users in the workspace.

Inputs:

- `limit` (int, optional) — Users per page (1–100, default: 20)
- `cursor` (string, optional) — Pagination cursor from a previous response

output:

{
  "ok": true,
  "members": [{ "id": "U123", "name":

Returns information about the Slack workspace including name, domain, and settings.

Inputs:

none

output:

{
  "ok": true,
  "team": {
    "id": "T123",
    "name": "My Company",
    "domain": "mycompany",
    "email_domain": "mycompany.com"

Returns the current presence status (active or away) of a workspace user.

Inputs:

- `user` (string, required) — Slack user ID (e.g., U123ABC456)

output:

{
  "ok": true,
  "presence": "active",
  "online": true,
  "auto_away": false
}

API Parameters Reference

Most tools accept either a channel ID or a channel name:

channel ID:   C123ABC456   (preferred — stable even if channel is renamed)
Channel name: #general     (convenient but can break if channel is renamed)

use list_channels or map_channels to look up channel IDs.

Slack uses Unix timestamps with microseconds as unique message identifiers:

format:  1234567890.123456
Example: 1712345678.000200

the ts field from any message response can be used to reply, update, delete, or identify a message. The thread_ts is the ts of the first message in a thread.

The blocks parameter accepts Slack Block Kit JSON for rich message formatting:

[
  {
    "type": "section",
    "text": { "type": "mrkdwn", "text": "*Hello!* This is bold." }
  }
]

full Block Kit reference: Slack Block Kit Builder

Troubleshooting

Resources

Slack API Documentation — Official API reference
Slack Web API Methods — Complete method reference
Slack Block Kit Builder — Visual block builder
FastMCP Docs — FastMCP specification
FastMCP Credentials — FastMCP Credentials package for credential handling

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