Slack MCP Server

What is Slack MCP Server about?

Slack MCP Server exposes a Model Context Protocol endpoint that lets applications interact with Slack workspaces. It can fetch channel, thread, DM, and group‑DM histories, perform smart pagination, search messages with rich filters, and (optionally) post new messages—all through standard MCP transports (Stdio or Server‑Sent Events).

How to use Slack MCP Server?

1. Configure authentication – supply either an OAuth xoxp-… token or the pair of browser tokens xoxc-… and xoxd-… via environment variables (SLACK_MCP_XOXP_TOKEN or SLACK_MCP_XOXC_TOKEN/SLACK_MCP_XOXD_TOKEN).
2. Set optional runtime options – port/host, proxy, custom User‑Agent, TLS settings, cache file locations, log level, etc., using the documented environment variables.
3. Start the server – run the Go server (e.g., go run mcp/mcp-server.go). The server listens on the configured host/port and accepts MCP connections over Stdio or SSE.
4. Consume MCP tools – client applications can call the provided tools (conversations_history, conversations_replies, conversations_search_messages, conversations_add_message, channels_list) to read or write Slack data.
5. Enable posting – to allow conversations_add_message, set SLACK_MCP_ADD_MESSAGE_TOOL (true, a whitelist of channel IDs, or a blacklist using !).

Key features of Slack MCP Server

• Stealth and OAuth modes – operate without installing a bot (stealth) or with secure OAuth tokens.
• Enterprise Slack support – custom User‑Agent and TLS options for restricted environments.
• Channel/Thread lookup by name – use #general or @username_dm instead of raw IDs.
• Smart history fetching – pagination by date ranges (1d, 7d, 1m) or message count.
• Advanced search – filter by channel, DM, user, date ranges, and thread‑only mode.
• DM & Group DM handling – full access to direct and multi‑person conversations.
• Embedded user info – messages include user metadata for better context.
• Caching – optional JSON caches for users and channels to speed up lookups.
• Multiple transports – Stdio for local tools, SSE for HTTP‑based clients.
• Proxy configuration – route outbound Slack API calls through a proxy.
• Fine‑grained posting control – safe default with optional enable‑by‑env.

Use cases of Slack MCP Server

• LLM‑powered assistants that need up‑to‑date Slack context without installing a bot.
• Customer support bots querying recent channel discussions or ticket threads.
• Analytics dashboards that pull channel statistics, member counts, and recent activity.
• Search‑as‑a‑service exposing Slack archives to downstream applications.
• Automation scripts that post status updates or reminders after explicit enablement.
• Enterprise compliance tools that need read‑only access to Slack data behind firewalls.

FAQ from the Slack MCP Server

Q: Which authentication tokens are required? A: Provide either an OAuth xoxp-… token or both the browser token xoxc-… and cookie token xoxd-…. At least one method must be set.

Q: How do I enable message posting? A: Set SLACK_MCP_ADD_MESSAGE_TOOL to true (all channels), a comma‑separated whitelist of channel IDs, or a !‑prefixed list to allow all except specified channels.

Q: Can the server run behind a corporate proxy? A: Yes. Define SLACK_MCP_PROXY with the proxy URL.

Q: What is the purpose of the users and channels caches? A: Caches reduce API calls on startup and enable tools to resolve #name or @handle without extra lookups. Paths are configurable via SLACK_MCP_USERS_CACHE and SLACK_MCP_CHANNELS_CACHE.

Q: Which transports are supported? A: Stdio (for local MCP clients) and Server‑Sent Events (SSE) for HTTP‑based clients. The transport is chosen by the client connection.

Q: How do I limit the server’s log verbosity? A: Set SLACK_MCP_LOG_LEVEL to debug, info, warn, error, panic, or fatal.

Q: Is this an official Slack product? A: No. It is an open‑source implementation released under the MIT license.

Slack MCP Server

Model Context Protocol (MCP) server for Slack Workspaces. The most powerful MCP Slack server — supports Stdio and SSE transports, proxy settings, DMs, Group DMs, Smart History fetch (by date or count), may work via OAuth or in complete stealth mode with no permissions and scopes in Workspace 😏.

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This feature-rich Slack MCP Server has:

• Stealth and OAuth Modes: Run the server without requiring additional permissions or bot installations (stealth mode), or use secure OAuth tokens for access without needing to refresh or extract tokens from the browser (OAuth mode).
• Enterprise Workspaces Support: Possibility to integrate with Enterprise Slack setups.
• Channel and Thread Support with #Name @Lookup: Fetch messages from channels and threads, including activity messages, and retrieve channels using their names (e.g., #general) as well as their IDs.
• Smart History: Fetch messages with pagination by date (d1, 7d, 1m) or message count.
• Search Messages: Search messages in channels, threads, and DMs using various filters like date, user, and content.
• Safe Message Posting: The conversations_add_message tool is disabled by default for safety. Enable it via an environment variable, with optional channel restrictions.
• DM and Group DM support: Retrieve direct messages and group direct messages.
• Embedded user information: Embed user information in messages, for better context.
• Cache support: Cache users and channels for faster access.
• Stdio/SSE Transports & Proxy Support: Use the server with any MCP client that supports Stdio or SSE transports, and configure it to route outgoing requests through a proxy if needed.

Analytics Demo

Add Message Demo

Tools

1. conversations_history:

Get messages from the channel (or DM) by channel_id, the last row/column in the response is used as 'cursor' parameter for pagination if not empty

• Parameters:
  • channel_id (string, required): - channel_id (string): ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm.
  • include_activity_messages (boolean, default: false): If true, the response will include activity messages such as channel_join or channel_leave. Default is boolean false.
  • cursor (string, optional): Cursor for pagination. Use the value of the last row and column in the response as next_cursor field returned from the previous request.
  • limit (string, default: "1d"): Limit of messages to fetch in format of maximum ranges of time (e.g. 1d - 1 day, 1w - 1 week, 30d - 30 days, 90d - 90 days which is a default limit for free tier history) or number of messages (e.g. 50). Must be empty when 'cursor' is provided.

2. conversations_replies:

Get a thread of messages posted to a conversation by channelID and thread_ts, the last row/column in the response is used as cursor parameter for pagination if not empty.

• Parameters:
  • channel_id (string, required): ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm.
  • thread_ts (string, required): Unique identifier of either a thread’s parent message or a message in the thread. ts must be the timestamp in format 1234567890.123456 of an existing message with 0 or more replies.
  • include_activity_messages (boolean, default: false): If true, the response will include activity messages such as 'channel_join' or 'channel_leave'. Default is boolean false.
  • cursor (string, optional): Cursor for pagination. Use the value of the last row and column in the response as next_cursor field returned from the previous request.
  • limit (string, default: "1d"): Limit of messages to fetch in format of maximum ranges of time (e.g. 1d - 1 day, 1w - 1 week, 30d - 30 days, 90d - 90 days which is a default limit for free tier history) or number of messages (e.g. 50). Must be empty when 'cursor' is provided.

3. conversations_add_message

Add a message to a public channel, private channel, or direct message (DM, or IM) conversation by channel_id and thread_ts.

Note: Posting messages is disabled by default for safety. To enable, set the SLACK_MCP_ADD_MESSAGE_TOOL environment variable. If set to a comma-separated list of channel IDs, posting is enabled only for those specific channels. See the Environment Variables section below for details.

• Parameters:
  • channel_id (string, required): ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm.
  • thread_ts (string, optional): Unique identifier of either a thread’s parent message or a message in the thread_ts must be the timestamp in format 1234567890.123456 of an existing message with 0 or more replies. Optional, if not provided the message will be added to the channel itself, otherwise it will be added to the thread.
  • payload (string, required): Message payload in specified content_type format. Example: 'Hello, world!' for text/plain or '# Hello, world!' for text/markdown.
  • content_type (string, default: "text/markdown"): Content type of the message. Default is 'text/markdown'. Allowed values: 'text/markdown', 'text/plain'.

4. conversations_search_messages

Search messages in a public channel, private channel, or direct message (DM, or IM) conversation using filters. All filters are optional, if not provided then search_query is required.

• Parameters:
  • search_query (string, optional): Search query to filter messages. Example: 'marketing report' or full URL of Slack message e.g. 'https://slack.com/archives/C1234567890/p1234567890123456', then the tool will return a single message matching given URL, herewith all other parameters will be ignored.
  • filter_in_channel (string, optional): Filter messages in a specific channel by its ID or name. Example: C1234567890 or #general. If not provided, all channels will be searched.
  • filter_in_im_or_mpim (string, optional): Filter messages in a direct message (DM) or multi-person direct message (MPIM) conversation by its ID or name. Example: D1234567890 or @username_dm. If not provided, all DMs and MPIMs will be searched.
  • filter_users_with (string, optional): Filter messages with a specific user by their ID or display name in threads and DMs. Example: U1234567890 or @username. If not provided, all threads and DMs will be searched.
  • filter_users_from (string, optional): Filter messages from a specific user by their ID or display name. Example: U1234567890 or @username. If not provided, all users will be searched.
  • filter_date_before (string, optional): Filter messages sent before a specific date in format YYYY-MM-DD. Example: 2023-10-01, July, Yesterday or Today. If not provided, all dates will be searched.
  • filter_date_after (string, optional): Filter messages sent after a specific date in format YYYY-MM-DD. Example: 2023-10-01, July, Yesterday or Today. If not provided, all dates will be searched.
  • filter_date_on (string, optional): Filter messages sent on a specific date in format YYYY-MM-DD. Example: 2023-10-01, July, Yesterday or Today. If not provided, all dates will be searched.
  • filter_date_during (string, optional): Filter messages sent during a specific period in format YYYY-MM-DD. Example: July, Yesterday or Today. If not provided, all dates will be searched.
  • filter_threads_only (boolean, default: false): If true, the response will include only messages from threads. Default is boolean false.
  • cursor (string, default: ""): Cursor for pagination. Use the value of the last row and column in the response as next_cursor field returned from the previous request.
  • limit (number, default: 20): The maximum number of items to return. Must be an integer between 1 and 100.

5. channels_list:

Get list of channels

• Parameters:
  • channel_types (string, required): Comma-separated channel types. Allowed values: mpim, im, public_channel, private_channel. Example: public_channel,private_channel,im
  • sort (string, optional): Type of sorting. Allowed values: popularity - sort by number of members/participants in each channel.
  • limit (number, default: 100): The maximum number of items to return. Must be an integer between 1 and 1000 (maximum 999).
  • cursor (string, optional): Cursor for pagination. Use the value of the last row and column in the response as next_cursor field returned from the previous request.

Resources

The Slack MCP Server exposes two special directory resources for easy access to workspace metadata:

1. slack://<workspace>/channels — Directory of Channels

Fetches a CSV directory of all channels in the workspace, including public channels, private channels, DMs, and group DMs.

• URI: slack://<workspace>/channels
• Format: text/csv
• Fields:
  • id: Channel ID (e.g., C1234567890)
  • name: Channel name (e.g., #general, @username_dm)
  • topic: Channel topic (if any)
  • purpose: Channel purpose/description
  • memberCount: Number of members in the channel

2. slack://<workspace>/users — Directory of Users

Fetches a CSV directory of all users in the workspace.

• URI: slack://<workspace>/users
• Format: text/csv
• Fields:
  • userID: User ID (e.g., U1234567890)
  • userName: Slack username (e.g., john)
  • realName: User’s real name (e.g., John Doe)

Setup Guide

• Authentication Setup
• Installation
• Configuration and Usage

Environment Variables (Quick Reference)

Variable	Required?	Default	Description
SLACK_MCP_XOXC_TOKEN	Yes*	nil	Slack browser token (xoxc-...)
SLACK_MCP_XOXD_TOKEN	Yes*	nil	Slack browser cookie d (xoxd-...)
SLACK_MCP_XOXP_TOKEN	Yes*	nil	User OAuth token (xoxp-...) — alternative to xoxc/xoxd
SLACK_MCP_PORT	No	13080	Port for the MCP server to listen on
SLACK_MCP_HOST	No	127.0.0.1	Host for the MCP server to listen on
SLACK_MCP_SSE_API_KEY	No	nil	Bearer token for SSE transport
SLACK_MCP_PROXY	No	nil	Proxy URL for outgoing requests
SLACK_MCP_USER_AGENT	No	nil	Custom User-Agent (for Enterprise Slack environments)
SLACK_MCP_CUSTOM_TLS	No	nil	Send custom TLS-handshake to Slack servers based on SLACK_MCP_USER_AGENT or default User-Agent. (for Enterprise Slack environments)
SLACK_MCP_SERVER_CA	No	nil	Path to CA certificate
SLACK_MCP_SERVER_CA_TOOLKIT	No	nil	Inject HTTPToolkit CA certificate to root trust-store for MitM debugging
SLACK_MCP_SERVER_CA_INSECURE	No	false	Trust all insecure requests (NOT RECOMMENDED)
SLACK_MCP_ADD_MESSAGE_TOOL	No	nil	Enable message posting via conversations_add_message by setting it to true for all channels, a comma-separated list of channel IDs to whitelist specific channels, or use ! before a channel ID to allow all except specified ones, while an empty value disables posting by default.
SLACK_MCP_ADD_MESSAGE_MARK	No	nil	When the conversations_add_message tool is enabled, any new message sent will automatically be marked as read.
SLACK_MCP_ADD_MESSAGE_UNFURLING	No	nil	Enable to let Slack unfurl posted links or set comma-separated list of domains e.g. github.com,slack.com to whitelist unfurling only for them. If text contains whitelisted and unknown domain unfurling will be disabled for security reasons.
SLACK_MCP_USERS_CACHE	No	.users_cache.json	Path to the users cache file. Used to cache Slack user information to avoid repeated API calls on startup.
SLACK_MCP_CHANNELS_CACHE	No	.channels_cache_v2.json	Path to the channels cache file. Used to cache Slack channel information to avoid repeated API calls on startup.
SLACK_MCP_LOG_LEVEL	No	info	Log-level for stdout or stderr. Valid values are: debug, info, warn, error, panic and fatal

*You need either xoxp or both xoxc/xoxd tokens for authentication.

Limitations matrix & Cache

Users Cache	Channels Cache	Limitations
:x:	:x:	No cache, No LLM context enhancement with user data, tool channels_list will be fully not functional. Tools conversations_* will have limited capabilities and you won't be able to search messages by @userHandle or #channel-name, getting messages by @userHandle or #channel-name won't be available either.
:white_check_mark:	:x:	No channels cache, tool channels_list will be fully not functional. Tools conversations_* will have limited capabilities and you won't be able to search messages by @userHandle or #channel-name, getting messages by @userHandle or #channel-name won't be available either.
:white_check_mark:	:white_check_mark:	No limitations, fully functional Slack MCP Server.

Debugging Tools

# Run the inspector with stdio transport
npx @modelcontextprotocol/inspector go run mcp/mcp-server.go --transport stdio

# View logs
tail -n 20 -f ~/Library/Logs/Claude/mcp*.log

Security

• Never share API tokens
• Keep .env files secure and private

License

Licensed under MIT - see LICENSE file. This is not an official Slack product.