slack

name	slack
description	Complete guide to all Slack tools — messaging, channels, users, search, files, reactions, and threads.
version	1.0.0
license	MIT
metadata	{"category":"Communication","difficulty":"beginner","apply-to":"slack_send_channel_message slack_reply_to_message slack_add_reaction slack_get_channel_history slack_get_reactions slack_get_thread_replies slack_send_dm slack_search_messages slack_get_user_info slack_upload_file slack-get-user slack-list-channels slack-send-message slack_create_channel slack_set_channel_topic slack_join_channel","author":"Matimo","tags":"slack,messaging,channels,communication"}

Slack

Complete guide to using Matimo's Slack tools for messaging, channels, users, search, and file sharing.

All Available Tools

Tool	Purpose	Category
slack_send_channel_message	Post a message to a channel	Messaging
slack_reply_to_message	Reply in a thread	Messaging
slack_add_reaction	Add an emoji reaction	Messaging
slack_get_reactions	Get reactions on a message	Messaging
slack_get_channel_history	Read recent messages from a channel	Messaging
slack_get_thread_replies	Get all replies in a thread	Messaging
slack_send_dm	Send a direct message to a user	Users
slack_search_messages	Search across all channels	Search
slack_get_user_info	Look up a user's profile	Users
slack-get-user	Get basic user details	Users
slack_upload_file	Upload a file to a channel or DM	Files
slack-list-channels	List available channels	Channels
slack-send-message	Send a message (simplified)	Messaging
slack_create_channel	Create a new channel	Channels
slack_set_channel_topic	Set or update the channel topic	Channels
slack_join_channel	Join an existing channel	Channels

Authentication

All Slack tools require a SLACK_BOT_TOKEN environment variable. The bot must have the relevant OAuth scopes (chat:write, channels:read, channels:history, users:read, search:read, files:write).

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Channel Messaging

Sending a Message

Use slack_send_channel_message to post to any public or private channel the bot is a member of.

Parameter	Type	Required	Description
channel	string	Yes	Channel ID (C01ABCDEF) or name (#general)
text	string	No	Plain-text message body
blocks	array	No	Block Kit UI layout for rich formatting

Best practices:

• Always provide text even with blocks — it's the notification preview and screen reader fallback
• Use channel IDs over names for reliability (names can change)
• Keep messages under 4000 characters; split longer content

{
  "channel": "C01ABCDEF",
  "text": "Deployment to production completed successfully :white_check_mark:"
}

Replying in Threads

Use slack_reply_to_message to keep conversations organized.

Parameter	Type	Required	Description
channel	string	Yes	Channel ID where the parent message lives
thread_ts	string	Yes	Timestamp of the parent message
text	string	Yes	Reply text

Use threads for follow-up info, status updates, and error details rather than cluttering the main channel.

Reactions

Use slack_add_reaction to acknowledge messages silently.

Parameter	Type	Required	Description
channel	string	Yes	Channel ID
timestamp	string	Yes	Message timestamp to react to
name	string	Yes	Emoji name without colons (e.g., thumbsup)

Common patterns: eyes = "looking into it", white_check_mark = "done", hourglass_flowing_sand = "working on it".

Reading History

Use slack_get_channel_history before responding to understand context.

Parameter	Type	Required	Description
channel	string	Yes	Channel ID
limit	number	No	Number of messages (default: 10, max: 100)

Always read channel history before sending to prevent duplicate messages.

---

Users

Direct Messages

Use slack_send_dm to message a user privately.

Parameter	Type	Required	Description
user_id	string	Yes	User ID (U01ABCDEF) — not email or display name
text	string	Yes	Message text

Use DMs for personal notifications and sensitive information. Use channels for team-wide announcements.

Looking Up Users

Use slack_get_user_info to retrieve profile data (name, email, timezone, status, bot/admin flags).

Finding User IDs

1. Use slack-get-user or slack_get_user_info to look up by name
2. Read channel history — messages include a user field
3. Slack profile URL: team.slack.com/team/U01ABCDEF

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Search

Use slack_search_messages to find messages across the workspace.

Parameter	Type	Required	Description
query	string	Yes	Search query with optional modifiers

Search modifiers: from:@user, in:#channel, before:YYYY-MM-DD, after:YYYY-MM-DD, has:link, has:reaction.

{ "query": "deployment failed in:#production after:2024-03-01" }

---

Channels

Listing Channels

Use slack-list-channels to discover existing channels before creating duplicates.

Creating a Channel

Use slack_create_channel with a name (lowercase, hyphens, max 80 chars) and optional is_private boolean.

Naming conventions: proj-{name}, team-{name}, incident-{id}, tmp-{name}, announce-{scope}.

Always search before creating. Set a topic immediately after creation.

Setting Topics

Use slack_set_channel_topic to describe channel purpose. Good topics include purpose, key links, and contact info.

Joining

Use slack_join_channel before reading history or sending messages. If you get not_in_channel, join first.

---

Files

Use slack_upload_file to share files in channels or DMs.

Parameter	Type	Required	Description
channels	string	Yes	Comma-separated channel IDs
content	string	Yes	File content (text-based)
filename	string	No	Filename (e.g., report.csv)
filetype	string	No	File type (csv, json, text)
title	string	No	File title

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Common Workflows

Notify Then Follow Up

1. Read channel history with slack_get_channel_history
2. Send notification with slack_send_channel_message
3. React with eyes on user's request
4. Reply with results in a thread
5. React with white_check_mark when done

Investigate and Report

1. Search for messages with slack_search_messages
2. Look up requesting user with slack_get_user_info
3. Read channel history for context
4. DM findings to user via slack_send_dm
5. Upload detailed report via slack_upload_file

Set Up a Project Channel

1. List existing channels to avoid duplicates
2. Create channel: proj-{project-name}
3. Set topic with purpose and links
4. Send introductory message

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Common Errors

Error	Cause	Fix
channel_not_found	Bot not a member	Invite: /invite @botname
not_in_channel	Bot hasn't joined	Use slack_join_channel first
invalid_blocks	Malformed Block Kit JSON	Validate at Slack Block Kit Builder
msg_too_long	Exceeds 40,000 chars	Split into multiple messages
user_not_found	Invalid user ID	Verify with slack_get_user_info
cannot_dm_bot	Trying to DM a bot	Only DM real users
name_taken	Channel name exists	List channels first
not_allowed_token_type	Missing OAuth scope	Reconfigure bot permissions