Slack CLI for AI Agents

CLIs are eating MCPs. The industry is converging on the very same idea. MCPs for all their merit can be token hungry, slow, and unreliable for complex tool chaining. However, coding agents have become incredibly good at working with CLIs, and in fact they are far more comfortable working with CLI tools than MCP. With Composio's Universal CLI, your coding agents can talk to over 1000+ SaaS applications. With Slack, agents can send reminder to marketing channel at 10am, add reaction to latest team message, archive inactive project channel after review, and more — all without worrying about authentication. This guide walks you through Composio Universal CLI and explains how you can connect it with coding agents like Claude Code, Codex, OpenCode, etc, for end-to-end Slack automation.

Slack logoSlack
Oauth2

Slack is a channel-based messaging platform for teams and organizations. It helps people collaborate in real time, share files, and connect all their tools in one place.

145 Tools8 Triggers

Introduction

CLIs are eating MCPs. The industry is converging on the very same idea. MCPs for all their merit can be token hungry, slow, and unreliable for complex tool chaining. However, coding agents have become incredibly good at working with CLIs, and in fact they are far more comfortable working with CLI tools than MCP.

With Composio's Universal CLI, your coding agents can talk to over 1000+ SaaS applications. With Slack, agents can send reminder to marketing channel at 10am, add reaction to latest team message, archive inactive project channel after review, and more — all without worrying about authentication.

This guide walks you through Composio Universal CLI and explains how you can connect it with coding agents like Claude Code, Codex, OpenCode, etc, for end-to-end Slack automation.

Also integrate Slack with

What is Universal CLI and why use it?

The idea behind building the universal CLI is to give agents a single command interface to interact with all your external applications. Here's what you'll get with it:

  • Agent-friendly: Coding agents like Claude Code, Codex, and OpenCode can use CLI tools natively — no MCP setup required.
  • Authentication handled: Connect once via OAuth or API Key, and all CLI commands work with your credentials automatically.
  • Tool discovery: Search, inspect, and execute 20,000+ tools across 1000+ apps from one interface.
  • Trigger support: Use triggers to listen for events across your apps, powered by real-time webhooks or polling under the hood.
  • Type generation: Generate typed schemas for autocomplete and type safety in your projects.

Prerequisites

Install the Composio CLI, authenticate, and initialize your project:

bash
# Install the Composio CLI
curl -fsSL https://composio.dev/install | bash

# Authenticate with Composio
composio login

During login you'll be redirected to sign in page, finish the complete flow and you're all set.

Composio CLI authentication flow

Connecting Slack to Coding Agents via Universal CLI

Once it is installed, it's essentially done. Claude Code, Codex, OpenCode, OpenClaw, or any other agent will be able to access the CLI. A few steps to give agents access to your apps.

  1. Launch your Coding Agent — Claude Code, Codex, OpenCode, anything you prefer.
  2. Prompt it to "Authenticate with Slack"
  3. Complete the authentication and authorization flow and your Slack integration is all set.
  4. Start asking anything you want.

Universal CLI Commands for Slack

You can also manually execute CLI commands to interact with your Slack.

Connect your Slack account

Link your Slack account and verify the connection:

bash
# Connect your Slack account (opens OAuth flow)
composio connected-accounts link slack

# Verify the connection
composio connected-accounts list --toolkits slack

Discover Slack tools

Search and inspect available Slack tools:

bash
# List all available Slack tools
composio tools list --toolkit slack

# Search for Slack tools by action
composio tools search "slack"

# Inspect a tool's input schema
composio tools info SLACK_ADD_AN_EMOJI_ALIAS_IN_SLACK

Common Slack Actions

Add an emoji aliasAdds an alias for an existing custom emoji in a slack enterprise grid organization

bash
composio tools execute SLACK_ADD_AN_EMOJI_ALIAS_IN_SLACK \
  --name "parrot_alias" \
  --token "<string>" \
  --alias_for "party_parrot"

Add a remote fileAdds a reference to an external file (e

bash
composio tools execute SLACK_ADD_A_REMOTE_FILE_FROM_A_SERVICE \
  --title "Project Proposal Q3.docx" \
  --token "xoxp-123456789012-123456789012-1234567890123-abcdefghijklmnopqrstuvwxyz123456" \
  --filetype "pdf" \
  --external_id "file-abc-123-xyz-789"

Add a star to an itemStars a channel, file, file comment, or a specific message in slack

bash
composio tools execute SLACK_ADD_A_STAR_TO_AN_ITEM \
  --file "F1234567890" \
  --channel "C1234567890" \
  --timestamp "1234567890.123456" \
  --file_comment "Fc1234567890"

Add call participantsRegisters new participants added to a slack call

bash
composio tools execute SLACK_ADD_CALL_PARTICIPANTS \
  --id "R0123456789" \
  --users "[{"slack_id": "U1H77", "external_id": "ext-id"}]"

Set up Slack Triggers

Listen for events in real time using triggers:

New Channel Created TriggerTriggered when a new channel is created in Slack

bash
# Find your connected account ID
composio connected-accounts list --toolkits slack

# Create a trigger
composio triggers create SLACK_CHANNEL_CREATED \
  --connected-account-id <your-connected-account-id> \
  --trigger-config '{}'

# Listen for trigger events in real time
composio triggers listen --toolkits slack --table

Reaction Added TriggerTriggered when a reaction is added to a message in Slack

bash
# Find your connected account ID
composio connected-accounts list --toolkits slack

# Create a trigger
composio triggers create SLACK_REACTION_ADDED \
  --connected-account-id <your-connected-account-id> \
  --trigger-config '{}'

# Listen for trigger events in real time
composio triggers listen --toolkits slack --table

Reaction Removed TriggerTriggered when a reaction is removed from a message

bash
# Find your connected account ID
composio connected-accounts list --toolkits slack

# Create a trigger
composio triggers create SLACK_REACTION_REMOVED \
  --connected-account-id <your-connected-account-id> \
  --trigger-config '{}'

# Listen for trigger events in real time
composio triggers listen --toolkits slack --table

Generate Type Definitions

Generate typed schemas for Slack tools to get autocomplete and type safety in your project:

bash
# Auto-detect language
composio generate --toolkits slack

# TypeScript
composio ts generate --toolkits slack

# Python
composio py generate --toolkits slack

Tips & Tricks

  • Always inspect a tool's input schema before executing: composio tools info <TOOL_NAME>
  • Pipe output with jq for better readability: composio tools execute TOOL_NAME -d '{}' | jq
  • Set COMPOSIO_API_KEY as an environment variable for CI/CD pipelines
  • Use composio dev logs tools to inspect execution logs and debug issues

Next Steps

  • Try asking your coding agent to perform various Slack operations
  • Explore cross-app workflows by connecting more toolkits
  • Set up triggers for real-time automation
  • Use composio generate for typed schemas in your projects
TOOLS & TRIGGERS

Supported Tools and Triggers

Every Slack action and event your agent gets out of the box.

Add call participants

Registers new participants added to a Slack call.

Add emoji

Adds a custom emoji to a Slack workspace given a unique name and an image URL; subject to workspace emoji limits.

Add an emoji alias

Adds an alias for an existing custom emoji in a Slack Enterprise Grid organization.

Add Enterprise user to workspace

Adds an Enterprise user to a workspace.

Add reaction to message

Adds a specified emoji reaction to an existing message in a Slack channel, identified by its timestamp; does not remove or retrieve reactions.

Add a remote file

Adds a reference to an external file (e.

Add a star to an item

Stars a channel, file, file comment, or a specific message in Slack.

Search for channels in Enterprise organization

Tool to search for public or private channels in an Enterprise organization.

Test Slack API connection

Tool to check API calling code by testing connectivity and authentication to the Slack API.

Archive a Slack conversation

Archives a Slack conversation by its ID, rendering it read-only and hidden while retaining history, ideal for cleaning up inactive channels; be aware that some channels (like #general or certain DMs) cannot be archived and this may impact connected integrations.

Real-time search

Search Slack messages, files, channels, and users via Real-time Search API.

Check search capabilities

Check if semantic (AI-powered) search is available on the Slack workspace.

Close conversation channel

Closes a Slack direct message (DM) or multi-person direct message (MPDM) channel, removing it from the user's sidebar without deleting history; this action affects only the calling user's view.

Convert public channel to private

Convert a public Slack channel to private using the Admin API.

Create a reminder

Creates a Slack reminder with specified text and time; time accepts Unix timestamps, seconds from now, or natural language (e.

Create Slack Canvas

Creates a new Slack Canvas with the specified title and optional content.

Create channel

Initiates a public or private channel-based conversation in a Slack workspace.

Create a channel-based conversation

Creates a new public or private Slack channel with a unique name; the channel can be org-wide, or team-specific if `team_id` is given (required if `org_wide` is false or not provided).

Create Enterprise team

Tool to create an Enterprise team in Slack.

Create a Slack user group

Creates a new User Group (often referred to as a subteam) in a Slack workspace.

Customize URL unfurl

Customizes URL previews (unfurling) in a specific Slack message using a URL-encoded JSON in `unfurls` to define custom content or remove existing previews.

Delete Slack Canvas

Deletes a Slack Canvas permanently and irreversibly.

Delete a public or private channel

Permanently and irreversibly deletes a specified public or private channel, including all its messages and files, within a Slack Enterprise Grid organization.

Delete a file by ID

Permanently deletes an existing file from a Slack workspace using its unique file ID; this action is irreversible and also removes any associated comments or shares.

Delete file comment

Deletes a specific comment from a file in Slack; this action is irreversible.

Delete a Slack reminder

Deletes an existing Slack reminder, typically when it is no longer relevant or a task is completed; this operation is irreversible.

Delete a message from a chat

Deletes a message, identified by its channel ID and timestamp, from a Slack channel, private group, or direct message conversation; the authenticated user or bot must be the original poster.

Delete scheduled chat message

Deletes a pending, unsent scheduled message from the specified Slack channel, identified by its `scheduled_message_id`.

Delete user profile photo

Deletes the Slack profile photo for the user identified by the token, reverting them to the default avatar; this action is irreversible and succeeds even if no custom photo was set.

Disable a Slack user group

Disables a specified, currently enabled Slack User Group by its unique ID, effectively archiving it by setting its 'date_delete' timestamp; the group is not permanently deleted and can be re-enabled.

Download Slack file

Tool to download Slack file content and convert it to a publicly accessible URL.

Edit Slack Canvas

Edits a Slack Canvas with granular control over content placement.

Share file public url

Enables public sharing for an existing Slack file by generating a publicly accessible URL; this action does not create new files.

Enable a user group

Enables a disabled User Group in Slack using its ID, reactivating it for mentions and permissions; this action only changes the enabled status and cannot create new groups or modify other properties.

End a call

Ends an ongoing Slack call, identified by its ID (obtained from `calls.

End DND session

Ends the authenticated user's current Do Not Disturb (DND) session in Slack, affecting only DND status and making them available; if DND is not active, Slack acknowledges the request without changing status.

End snooze

Ends the current user's snooze mode immediately.

Fetch conversation history

Fetches a chronological list of messages and events from a specified Slack conversation, accessible by the authenticated user/bot, with options for pagination and time range filtering.

Fetch item reactions

Fetches reactions for a Slack message, file, or file comment.

Retrieve conversation replies

Retrieves replies to a specific parent message in a Slack conversation, using the channel ID and the parent message's timestamp (`ts`).

Fetch team info

Fetches comprehensive metadata about the current Slack team, or a specified team if the provided ID is accessible.

Find channels

Find channels in a Slack workspace by any criteria - name, topic, purpose, or description.

Lookup users by email

Retrieves the Slack user object for an active user by their registered email address; requires the users:read.

Find users

Find users in a Slack workspace by any criteria - email, name, display name, or other text.

Get Audit Action Types

Tool to retrieve information about action types available in the Slack Audit Logs API.

Get Audit Schemas

Tool to retrieve object schema information from the Slack Audit Logs API.

Fetch bot user information

Fetches information for a specified, existing Slack bot user; will not work for regular user accounts or other integration types.

Retrieve call information

Retrieves a point-in-time snapshot of a specific Slack call's information.

Get channel conversation preferences

Retrieves conversation preferences (e.

Get reminder information

Retrieves detailed information for an existing Slack reminder specified by its ID; this is a read-only operation.

Get remote file

Retrieve information about a remote file added to Slack via the files.

Retrieve team profile details

Retrieves all profile field definitions for a Slack team, optionally filtered by visibility, to understand the team's profile structure.

Get team DND status

Retrieves a user's current Do Not Disturb status.

Retrieve user presence

Retrieves a Slack user's current real-time presence (e.

Get workspace connections for channel

Tool to get all workspaces a channel is connected to within an Enterprise org.

Fetch workspace settings information

Retrieves detailed settings for a specific Slack workspace, primarily for administrators in an Enterprise Grid organization to view or audit workspace configurations.

Invite users to a Slack channel

Invites users to an existing Slack channel using their valid Slack User IDs.

Invite users to channel

Invites users to a specified Slack channel; this action is restricted to Enterprise Grid workspaces and requires the authenticated user to be a member of the target channel.

Invite user to workspace

Invites a user to a Slack workspace and specified channels by email; use `resend=True` to re-process an existing invitation for a user not yet signed up.

Join conversation by channel id

Joins an existing Slack conversation (public channel, private channel, or multi-person direct message) by its ID, if the authenticated user has permission.

Leave conversation channel

Leaves a Slack conversation given its channel ID; fails if leaving as the last member of a private channel or if used on a Slack Connect channel.

List approved apps

Tool to list approved apps for an Enterprise Grid organization or workspace.

List app requests

Tool to list pending app installation requests for a team/workspace.

List admin emoji

List custom emoji across an Enterprise Grid organization.

List all channels

Lists conversations available to the user with various filters and search options.

List all users

Retrieves a paginated list of all users with profile details, status, and team memberships in a Slack workspace; data may not be real-time.

List approved workspace invite requests

List all approved workspace invite requests with pagination support.

List authorized teams

Obtains a paginated list of workspaces your org-wide app has been approved for.

List conversations

List conversations (channels/DMs) accessible to a specified user (or the authenticated user if no user ID is provided), respecting shared membership for non-public channels.

List team custom emojis

Retrieves all custom emojis for the Slack workspace (image URLs or aliases), not standard Unicode emojis; does not include usage statistics or creation dates.

List denied workspace invite requests

Tool to list all denied workspace invite requests with details about who denied them and when.

List Enterprise teams

List all teams (workspaces) in a Slack Enterprise Grid organization with pagination support.

List Slack files

Lists files and their metadata within a Slack workspace, filterable by user, channel, timestamp, or type; returns metadata only, not file content.

List IDP groups linked to channel

Lists IDP groups that have restricted access to a private Slack channel.

List pending workspace invite requests

Tool to list all pending workspace invite requests.

List pinned items in a channel

Retrieves all messages and files pinned to a specified channel; the caller must have access to this channel.

List reminders

Lists all reminders with their details for the authenticated Slack user; returns an empty array if no reminders exist (valid state, not an error).

List remote files

Retrieve information about a team's remote files.

List Restricted Apps

Tool to list restricted apps for an org or workspace.

List scheduled messages

Retrieves a list of pending (not yet delivered) messages scheduled in a specific Slack channel, or across all accessible channels if no channel ID is provided, optionally filtered by time and paginated.

List starred items

Lists items starred by a user.

List all users in a user group

Retrieves a list of all user IDs within a specified Slack user group, with an option to include users from disabled groups.

List user groups

Lists user groups in a Slack workspace, including user-created and default groups; results for large workspaces may be paginated.

List user reactions

Lists all reactions added by a specific user to messages, files, or file comments in Slack, useful for engagement analysis when the item content itself is not required.

List workspace admins

Tool to list all admins on a given Slack workspace.

List workspace owners

Tool to list all owners on a given Slack workspace.

List admin users

Retrieves a paginated list of admin users for a specified Slack workspace.

Lookup Canvas Sections

Looks up section IDs in a Slack Canvas for use with targeted edit operations.

Open DM

Opens or resumes a Slack direct message (DM) or multi-person direct message (MPIM) by providing either user IDs or an existing channel ID.

Pin an item to a channel

Pins a message to a specified Slack channel; the message must not already be pinned.

Read Audit Logs

Read Slack Enterprise Grid Audit Logs (logins, admin changes, app installs, channel/privacy changes, etc.

Remove call participants

Registers participants removed from a Slack call.

Remove emoji

Tool to remove a custom emoji across an Enterprise Grid organization.

Remove reaction from item

Removes an emoji reaction from a message, file, or file comment in Slack.

Remove remote file

Removes the Slack reference to an external file (which must have been previously added via the remote files API), specified by either its `external_id` or `file` ID (one of which is required), without deleting the actual external file.

Remove a star from an item

Removes a star from a previously starred Slack item (message, file, file comment, channel, group, or DM), requiring identification via `file`, `file_comment`, `channel` (for channel/group/DM), or both `channel` and `timestamp` (for a message).

Remove user from conversation

Removes a specified user from a Slack conversation (channel); the caller must have permissions to remove users and cannot remove themselves using this action.

Remove user from workspace

Tool to remove a user from a Slack workspace.

Rename a conversation

Renames a Slack channel, automatically adjusting the new name to meet naming conventions (e.

Rename an emoji

Renames an existing custom emoji in a Slack workspace, updating all its instances.

Reset user sessions

Tool to wipe all valid sessions on all devices for a given user.

Restrict app installation

Restrict an app for installation on a workspace.

Retrieve a user's identity details

Retrieves the authenticated user's and their team's identity, with details varying based on OAuth scopes (e.

Retrieve conversation information

Retrieves metadata for a Slack conversation by ID (e.

Get conversation members

Retrieves a paginated list of active member IDs (not names, emails, or presence) for a specified Slack public channel, private channel, DM, or MPIM.

Retrieve user DND status

Retrieves a Slack user's current Do Not Disturb (DND) status to determine their availability before interaction; any specified user ID must be a valid Slack user ID.

Retrieve detailed file information

Retrieves detailed metadata and paginated comments for a specific Slack file ID; does not download file content.

Retrieve detailed user information

Retrieves comprehensive information for a valid Slack user ID, excluding message history and channel memberships.

Retrieve message permalink

Retrieves a permalink URL for a specific message in a Slack channel or conversation; the permalink respects Slack's privacy settings.

Retrieve user profile information

Retrieves profile information for a specified Slack user (defaults to the authenticated user if `user` ID is omitted); a provided `user` ID must be valid.

Revoke a file's public url

Revokes a Slack file's public URL, making it private; this is a no-op if not already public and is irreversible.

Start RTM session

Starts a Real Time Messaging session and returns a WebSocket URL.

Schedule message

Schedules a message to a Slack channel, DM, or private group for a future time (`post_at`), requiring `text`, `blocks`, or `attachments` for content; scheduling is limited to 120 days in advance.

Get SCIM service provider configuration

Tool to retrieve SCIM service provider configuration from Slack.

Search all content

Tool to search all messages and files.

Search messages

Workspace‑wide Slack message search with date ranges and filters.

Send ephemeral message

Sends an ephemeral message visible only to the specified `user` in a channel; other channel members cannot see it.

Share a me message in a channel

Sends a 'me message' (e.

Send message

Posts a message to a Slack channel, DM, or private group; requires at least one content field (`markdown_text`, `text`, `blocks`, or `attachments`) — omitting all causes a `no_text` error.

Set admin user

Promotes an existing workspace member (guest, regular user, or owner) to admin status.

Set conversation preferences

Sets the posting permissions for a public or private channel in Slack.

Set a conversation's purpose

Sets the purpose (a short description of its topic/goal, displayed in the header) for a Slack conversation; the calling user must be a member.

Set default channels

Tool to set the default channels of a workspace.

Set DND duration

Turns on Do Not Disturb mode for the current user, or changes its duration.

Set profile photo

This method allows the user to set their profile image.

Set conversation read cursor

Marks a message, specified by its timestamp (`ts`), as the most recently read for the authenticated user in the given `channel`, provided the user is a member of the channel and the message exists within it.

Set conversation topic

Sets or updates the topic for a specified Slack conversation.

Set user presence

Manually sets a user's Slack presence, overriding automatic detection; this setting persists across connections but can be overridden by user actions or Slack's auto-away (e.

Set Slack user profile information

Updates a Slack user's profile, setting either individual fields or multiple fields via a JSON object.

Set workspace description

Set the description of a given workspace.

Set workspace icon

Sets the icon of a workspace.

Set workspace name

Set the name of a given Slack workspace.

Set workspace owner

Set an existing guest, regular user, or admin user to be a workspace owner.

Set workspaces for channel

Set the workspaces in an Enterprise grid org that connect to a channel.

Share a remote file in channels

Shares a remote file, which must already be registered with Slack, into specified Slack channels or direct message conversations.

Start call

Registers a new call in Slack using `calls.

Test authentication

Checks authentication and tells you who you are.

Unarchive channel

Reverses conversation archival.

Unpin message from channel

Unpins a message, identified by its timestamp, from a specified channel if the message is currently pinned there; this operation is destructive.

Update call information

Updates the title, join URL, or desktop app join URL for an existing Slack call identified by its ID.

Update an existing remote file

Updates metadata or content details for an existing remote file in Slack; this action cannot upload new files or change the fundamental file type.

Update a Slack message

Updates a Slack message, identified by `channel` ID and `ts` timestamp, by modifying its `text`, `attachments`, or `blocks`; provide at least one content field, noting `attachments`/`blocks` are replaced if included (`[]` clears them).

Update Slack user group

Updates an existing Slack User Group, which must be specified by an existing `usergroup` ID, with new optional details such as its name, description, handle, or default channels.

Update user group members

Replaces all members of an existing Slack User Group with a new list of valid user IDs.

Upload or create a file in Slack

Upload files, images, screenshots, documents, or any media to Slack channels or threads.

FAQ

Frequently asked questions

The Composio Universal CLI is a single command-line interface that lets coding agents and developers interact with 1000+ SaaS applications. It handles authentication, tool discovery, action execution, and trigger setup — all from the terminal, without needing to configure MCP servers.

Any coding agent that can run shell commands works with the Composio CLI — including Claude Code, Codex, OpenCode, OpenClaw, and others. Once the CLI is installed, agents automatically discover and use the composio commands to interact with Slack and other connected apps.

MCP servers require configuration and can be token-heavy for complex workflows. The CLI gives agents a direct, lightweight interface — no server setup needed. Agents simply call composio commands like any other shell tool. It's faster to set up, more reliable for multi-step tool chaining, and works natively with how coding agents already operate.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Slack data and credentials are handled as safely as possible. You can also bring your own OAuth credentials for full control.

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