Slack Automation via Rube MCP

Automate Slack workspace operations including messaging, search, channel management, and reaction workflows through Composio's Slack toolkit.

Prerequisites

• Rube MCP must be connected (RUBESEARCHTOOLS available)
• Active Slack connection via RUBEMANAGECONNECTIONS with toolkit slack
• Always call RUBESEARCHTOOLS first to get current tool schemas

Setup

Get Rube MCP: Add https://rube.app/mcp as an MCP server in your client configuration. No API keys needed — just add the endpoint and it works.

1. Verify Rube MCP is available by confirming RUBESEARCHTOOLS responds
2. Call RUBEMANAGECONNECTIONS with toolkit slack
3. If connection is not ACTIVE, follow the returned auth link to complete Slack OAuth
4. Confirm connection status shows ACTIVE before running any workflows

Core Workflows

1. Send Messages to Channels

When to use: User wants to post a message to a Slack channel or DM

Tool sequence:

1. SLACKFINDCHANNELS - Resolve channel name to channel ID [Prerequisite]
2. SLACKLISTALLCHANNELS - Fallback if FINDCHANNELS returns empty/ambiguous results [Fallback]
3. SLACKFINDUSERS - Resolve user for DMs or @mentions [Optional]
4. SLACKOPENDM - Open/reuse a DM channel if messaging a user directly [Optional]
5. SLACKSENDMESSAGE - Post the message with resolved channel ID [Required]
6. SLACKUPDATESASLACKMESSAGE - Edit the posted message if corrections needed [Optional]

Key parameters:

• channel: Channel ID or name (without '#' prefix)
• markdown_text: Preferred field for formatted messages (supports headers, bold, italic, code blocks)
• text: Raw text fallback (deprecated in favor of markdown_text)
• thread_ts: Timestamp of parent message to reply in a thread
• blocks: Block Kit layout blocks (deprecated, use markdown_text)

Pitfalls:

• SLACKFINDCHANNELS requires query param; missing it errors with "Invalid request data provided"
• SLACKSENDMESSAGE requires valid channel plus one of markdown_text/text/blocks/attachments
• Invalid block payloads return error=invalid_blocks (max 50 blocks)
• Replies become top-level posts if thread_ts is omitted
• Persist response.data.channel and response.data.message.ts from SEND_MESSAGE for edit/thread operations

2. Search Messages and Conversations

When to use: User wants to find specific messages across the workspace

Tool sequence:

1. SLACKFINDCHANNELS - Resolve channel for scoped search with in:#channel [Optional]
2. SLACKFINDUSERS - Resolve user for author filter with from:@user [Optional]
3. SLACKSEARCHMESSAGES - Run keyword search across accessible conversations [Required]
4. SLACKFETCHMESSAGETHREADFROMACONVERSATION - Expand threads for relevant hits [Required]

Key parameters:

• query: Search string supporting modifiers (in:#channel, from:@user, before:YYYY-MM-DD, after:YYYY-MM-DD, has:link, has:file)
• count: Results per page (max 100), or total with auto_paginate=true
• sort: 'score' (relevance) or 'timestamp' (chronological)
• sort_dir: 'asc' or 'desc'

Pitfalls:

• Validation fails if query is missing/empty
• ok=true can still mean no hits (response.data.messages.total=0)
• Matches are under response.data.messages.matches (sometimes also response.data_preview.messages.matches)
• match.text may be empty/truncated; key info can appear in matches[].attachments[]
• Thread expansion via FETCHMESSAGETHREAD can truncate when response.data.hasmore=true; paginate via responsemetadata.next_cursor

3. Manage Channels and Users

When to use: User wants to list channels, users, or workspace info

Tool sequence:

1. SLACKFETCHTEAM_INFO - Validate connectivity and get workspace identity [Required]
2. SLACKLISTALL_CHANNELS - Enumerate public channels [Required]
3. SLACKLISTCONVERSATIONS - Include private channels and DMs [Optional]
4. SLACKLISTALL_USERS - List workspace members [Required]
5. SLACKRETRIEVECONVERSATION_INFORMATION - Get detailed channel metadata [Optional]
6. SLACKLISTUSERGROUPSFORTEAMWITH_OPTIONS - List user groups [Optional]

Key parameters:

• cursor: Pagination cursor from responsemetadata.nextcursor
• limit: Results per page (default varies; set explicitly for large workspaces)
• types: Channel types filter ('publicchannel', 'privatechannel', 'im', 'mpim')

Pitfalls:

• Workspace metadata is nested under response.data.team, not top-level
• SLACKLISTALLCHANNELS returns public channels only; use SLACKLIST_CONVERSATIONS for private/IM coverage
• SLACKLISTALL_USERS can hit HTTP 429 rate limits; honor Retry-After header
• Always paginate via responsemetadata.nextcursor until empty; de-duplicate by id

4. React to and Thread Messages

When to use: User wants to add reactions or manage threaded conversations

Tool sequence:

1. SLACKSEARCHMESSAGES or SLACKFETCHCONVERSATION_HISTORY - Find the target message [Prerequisite]
2. SLACKADDREACTIONTOAN_ITEM - Add an emoji reaction [Required]
3. SLACKFETCHITEM_REACTIONS - List reactions on a message [Optional]
4. SLACKREMOVEREACTIONFROMITEM - Remove a reaction [Optional]
5. SLACKSENDMESSAGE - Reply in thread using thread_ts [Optional]
6. SLACKFETCHMESSAGETHREADFROMACONVERSATION - Read full thread [Optional]

Key parameters:

• channel: Channel ID where the message lives
• timestamp / ts: Message timestamp (unique identifier like '1234567890.123456')
• name: Emoji name without colons (e.g., 'thumbsup', 'wave::skin-tone-3')
• thread_ts: Parent message timestamp for threaded replies

Pitfalls:

• Reactions require exact channel ID + message timestamp pair
• Emoji names use Slack's naming convention without colons
• SLACKFETCHCONVERSATION_HISTORY only returns main channel timeline, NOT threaded replies
• Use SLACKFETCHMESSAGETHREADFROMACONVERSATION with parent's thread_ts to get thread replies

5. Schedule Messages

When to use: User wants to schedule a message for future delivery

Tool sequence:

1. SLACKFINDCHANNELS - Resolve channel ID [Prerequisite]
2. SLACKSCHEDULEMESSAGE - Schedule the message with post_at timestamp [Required]

Key parameters:

• channel: Resolved channel ID
• post_at: Unix timestamp for delivery (up to 120 days in advance)
• text / blocks: Message content

Pitfalls:

• Scheduling is limited to 120 days in advance
• post_at must be a Unix timestamp, not ISO 8601

Common Patterns

ID Resolution

Always resolve display names to IDs before operations:

• Channel name -> Channel ID: SLACKFINDCHANNELS with query param
• User name -> User ID: SLACKFINDUSERS with search_query or email
• DM channel: SLACKOPENDM with resolved user IDs

Pagination

Most list endpoints use cursor-based pagination:

• Follow responsemetadata.nextcursor until empty
• Set explicit limit values (e.g., 100-200) for reliable paging
• De-duplicate results by id across pages

Message Formatting

• Prefer markdown_text over text or blocks for formatted messages
• Use <@USER_ID> format to mention users (not @username)
• Use \n for line breaks in markdown_text

Known Pitfalls

• Channel resolution: SLACKFINDCHANNELS can return empty results if channel is private and bot hasn't been invited
• Rate limits: SLACKLISTALL_USERS and other list endpoints can hit HTTP 429; honor Retry-After header
• Nested responses: Results may be nested under response.data.results[0].response.data in wrapped executions
• Thread vs channel: SLACKFETCHCONVERSATIONHISTORY returns main timeline only; use SLACKFETCHMESSAGETHREADFROMA_CONVERSATION for thread replies
• Message editing: Requires both channel and original message ts; persist these from SEND_MESSAGE response
• Search delays: Recently posted messages may not appear in search results immediately
• Scope limitations: Missing OAuth scopes can cause 403 errors; check with SLACKGETAPPPERMISSIONSCOPES

Quick Reference

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Example

User request:

Automate Slack workspace operations including messaging, search, channel management, and reaction workflows through Composio's Slack toolkit.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.