Slack Automation via Rube MCP

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

Toolkit docs: composio.dev/toolkits/slack

Prerequisites

Rube MCP must be connected (RUBE_SEARCH_TOOLS available)
Active Slack connection via
```
RUBE_MANAGE_CONNECTIONS
```
with toolkit
```
slack
```
Always call
```
RUBE_SEARCH_TOOLS
```
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.

Verify Rube MCP is available by confirming
```
RUBE_SEARCH_TOOLS
```
responds
Call
```
RUBE_MANAGE_CONNECTIONS
```
with toolkit
```
slack
```
If connection is not ACTIVE, follow the returned auth link to complete Slack OAuth
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:

```
SLACK_FIND_CHANNELS
```
- Resolve channel name to channel ID [Prerequisite]
```
SLACK_LIST_ALL_CHANNELS
```
- Fallback if FIND_CHANNELS returns empty/ambiguous results [Fallback]
```
SLACK_FIND_USERS
```
- Resolve user for DMs or @mentions [Optional]
```
SLACK_OPEN_DM
```
- Open/reuse a DM channel if messaging a user directly [Optional]
```
SLACK_SEND_MESSAGE
```
- Post the message with resolved channel ID [Required]
```
SLACK_UPDATES_A_SLACK_MESSAGE
```
- 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:

```
SLACK_FIND_CHANNELS
```
requires
```
query
```
param; missing it errors with "Invalid request data provided"
```
SLACK_SEND_MESSAGE
```
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:

```
SLACK_FIND_CHANNELS
```
- Resolve channel for scoped search with
```
in:#channel
```
[Optional]
```
SLACK_FIND_USERS
```
- Resolve user for author filter with
```
from:@user
```
[Optional]
```
SLACK_SEARCH_MESSAGES
```
- Run keyword search across accessible conversations [Required]

SLACK_FETCH_MESSAGE_THREAD_FROM_A_CONVERSATION

- 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 FETCH_MESSAGE_THREAD can truncate when
```
response.data.has_more=true
```
; paginate via
```
response_metadata.next_cursor
```

3. Manage Channels and Users

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

Tool sequence:

```
SLACK_FETCH_TEAM_INFO
```
- Validate connectivity and get workspace identity [Required]
```
SLACK_LIST_ALL_CHANNELS
```
- Enumerate public channels [Required]
```
SLACK_LIST_CONVERSATIONS
```
- Include private channels and DMs [Optional]
```
SLACK_LIST_ALL_USERS
```
- List workspace members [Required]
```
SLACK_RETRIEVE_CONVERSATION_INFORMATION
```
- Get detailed channel metadata [Optional]

SLACK_LIST_USER_GROUPS_FOR_TEAM_WITH_OPTIONS

- List user groups [Optional]

Key parameters:

```
cursor
```
: Pagination cursor from
```
response_metadata.next_cursor
```
```
limit
```
: Results per page (default varies; set explicitly for large workspaces)
```
types
```
: Channel types filter ('public_channel', 'private_channel', 'im', 'mpim')

Pitfalls:

Workspace metadata is nested under
```
response.data.team
```
, not top-level
```
SLACK_LIST_ALL_CHANNELS
```
returns public channels only; use
```
SLACK_LIST_CONVERSATIONS
```
for private/IM coverage
```
SLACK_LIST_ALL_USERS
```
can hit HTTP 429 rate limits; honor Retry-After header
Always paginate via
```
response_metadata.next_cursor
```
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:

SLACK_SEARCH_MESSAGES

SLACK_FETCH_CONVERSATION_HISTORY

- Find the target message [Prerequisite]

```
SLACK_ADD_REACTION_TO_AN_ITEM
```
- Add an emoji reaction [Required]
```
SLACK_FETCH_ITEM_REACTIONS
```
- List reactions on a message [Optional]
```
SLACK_REMOVE_REACTION_FROM_ITEM
```
- Remove a reaction [Optional]
```
SLACK_SEND_MESSAGE
```
- Reply in thread using
```
thread_ts
```
[Optional]

SLACK_FETCH_MESSAGE_THREAD_FROM_A_CONVERSATION

- 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
```
SLACK_FETCH_CONVERSATION_HISTORY
```
only returns main channel timeline, NOT threaded replies

Use

SLACK_FETCH_MESSAGE_THREAD_FROM_A_CONVERSATION

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:

```
SLACK_FIND_CHANNELS
```
- Resolve channel ID [Prerequisite]
```
SLACK_SCHEDULE_MESSAGE
```
- 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:
```
SLACK_FIND_CHANNELS
```
with
```
query
```
param
User name -> User ID:
```
SLACK_FIND_USERS
```
with
```
search_query
```
or
```
email
```
DM channel:
```
SLACK_OPEN_DM
```
with resolved user IDs

Pagination

Most list endpoints use cursor-based pagination:

Follow
```
response_metadata.next_cursor
```
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:
```
SLACK_FIND_CHANNELS
```
can return empty results if channel is private and bot hasn't been invited
Rate limits:
```
SLACK_LIST_ALL_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:

SLACK_FETCH_CONVERSATION_HISTORY

returns main timeline only; use

SLACK_FETCH_MESSAGE_THREAD_FROM_A_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
```
SLACK_GET_APP_PERMISSION_SCOPES
```

Quick Reference

Task	Tool Slug	Key Params
Find channels	`SLACK_FIND_CHANNELS`	`query`
List all channels	`SLACK_LIST_ALL_CHANNELS`	`limit` , `cursor` , `types`
Send message	`SLACK_SEND_MESSAGE`	`channel` , `markdown_text`
Edit message	`SLACK_UPDATES_A_SLACK_MESSAGE`	`channel` , `ts` , `markdown_text`
Search messages	`SLACK_SEARCH_MESSAGES`	`query` , `count` , `sort`
Get thread	`SLACK_FETCH_MESSAGE_THREAD_FROM_A_CONVERSATION`	`channel` , `ts`
Add reaction	`SLACK_ADD_REACTION_TO_AN_ITEM`	`channel` , `name` , `timestamp`
Find users	`SLACK_FIND_USERS`	`search_query` or `email`
List users	`SLACK_LIST_ALL_USERS`	`limit` , `cursor`
Open DM	`SLACK_OPEN_DM`	user IDs
Schedule message	`SLACK_SCHEDULE_MESSAGE`	`channel` , `post_at` , `text`
Get channel info	`SLACK_RETRIEVE_CONVERSATION_INFORMATION`	channel ID
Channel history	`SLACK_FETCH_CONVERSATION_HISTORY`	`channel` , `oldest` , `latest`
Workspace info	`SLACK_FETCH_TEAM_INFO`	(none)

slack-automation

NPX Install

Tags

SKILL.md Content

Slack Automation via Rube MCP

Prerequisites

Setup

Core Workflows

1. Send Messages to Channels

2. Search Messages and Conversations

3. Manage Channels and Users

4. React to and Thread Messages

5. Schedule Messages

Common Patterns

ID Resolution

Pagination

Message Formatting

Known Pitfalls

Quick Reference