MCP Slack

io.github.crunchtoolsPublished by GitHub account crunchtoolsv0.1.2Updated Oct 24, 2026

Secure read-only MCP server for Slack workspaces

VerifiedSTDIODesktop onlyCommunication & Collaboration

Overview

AI-generated overview

Read Slack channels, messages, users, and files, and schedule or send messages, from an MCP client.

What you can do
A local MCP server that gives an assistant read access to a Slack workspace: listing channels, reading channel history and thread replies, searching messages, viewing reactions, stars, users, profiles, and file metadata. Two write tools schedule a message a configurable delay ahead or post it immediately, and cancel a scheduled message. It talks to Slack over HTTP directly rather than through an SDK.
When to use it
Useful when an assistant needs to look things up in Slack — recent channel activity, a thread, a person, or a file — or to send a message with a short window to cancel it. It is not for editing or deleting existing Slack content.
Requirements
Runs locally as a Python package (uvx or uv) or a container. Needs one of two mutually exclusive credentials: SLACK_USER_TOKEN (a user OAuth token from a Slack app), or the cookie pair SLACK_COOKIE_TOKEN and SLACK_COOKIE_D. Optional SLACK_ADD_MESSAGE_DELAY controls message scheduling. Network access to Slack is required.
Before you install
Cookie mode uses live browser session credentials (SLACK_COOKIE_TOKEN, SLACK_COOKIE_D) that let anything holding them act as the user with full access; they expire with the browser session and Slack can invalidate them at any time. Prefer SLACK_USER_TOKEN where a Slack app can be installed. The two write tools send or cancel messages and need the chat:write scope; messages are scheduled ahead by default, giving a cancel window.

Installation

In SourceWeft

  1. Open MCP Slack in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

mcp-slack-crunchtools

Secure MCP server for Slack workspaces. Provides Claude Code (and other MCP clients) with read access to your Slack channels, messages, users, and files, and can send a message on your behalf.

Features

  • Mostly read: 15 of the 17 tools only read and publish readOnlyHint: true. The other two send a message and cancel a scheduled one; nothing edits or deletes existing content.
  • Secure: 6-layer security model (input validation, token handling, client hardening, output sanitization, runtime protection, supply chain security).
  • User OAuth Token: Uses xoxp- tokens for user-scoped access to your workspace.
  • No SDK dependency: Uses httpx directly for minimal, auditable HTTP calls.

Quick Start

Using uvx (Recommended)

bash
claude mcp add mcp-slack-crunchtools \    --env SLACK_USER_TOKEN=xoxp-your-token \    -- uvx mcp-slack-crunchtools

Using Container

bash
claude mcp add mcp-slack-crunchtools \    --env SLACK_USER_TOKEN=xoxp-your-token \    -- podman run -i --rm -e SLACK_USER_TOKEN quay.io/crunchtools/mcp-slack

Local Development

bash
claude mcp add mcp-slack-crunchtools \    --env SLACK_USER_TOKEN=xoxp-your-token \    -- uv run mcp-slack-crunchtools

Setup

See CLAUDE.md for detailed instructions on creating a Slack app and obtaining a User OAuth Token.

Configuration

Authentication uses one of two mutually exclusive modes. The server picks cookie mode when both cookie variables are set, and token mode otherwise.

VariableRequiredDefaultDescription
SLACK_USER_TOKENtoken mode—User OAuth token (xoxp-...) from a Slack app installed in the workspace.
SLACK_COOKIE_TOKENcookie mode—Browser session token (xoxc-...). Must be paired with SLACK_COOKIE_D.
SLACK_COOKIE_Dcookie mode—Value of the d cookie (xoxd-...) from the same browser session. Sent as a Cookie: header alongside SLACK_COOKIE_TOKEN.
SLACK_ADD_MESSAGE_DELAYno3mHow far ahead outgoing messages are scheduled, giving you a window to cancel one. Duration string: 30s, 5m, 2h, or a bare integer for seconds. Set to 0, 0s, none, or false to disable scheduling and post immediately.

Which auth mode to use

Cookie mode is the working path for this deployment. Token mode requires a Slack app to be created and approved in the workspace; where that approval is not available, cookie mode is the only way to authenticate at all.

Cookie mode borrows an existing browser session rather than holding a credential issued to an application. That has consequences worth stating plainly:

  • Both values are live session credentials. Anything holding them can act as you in Slack, with your full access. Treat them exactly as you would your password.
  • They expire when the browser session does, so cookie mode needs periodic re-extraction. A sudden wave of auth failures usually means the session rotated, not that the server broke.
  • Slack does not issue these for programmatic use and can invalidate them at any time. Cookie mode is a workaround for the absence of an approved app, not a supported integration path.

Prefer SLACK_USER_TOKEN whenever a Slack app can actually be installed.

Tools

ToolDescription
slack_auth_testTest connection and get token owner info
slack_list_channelsList workspace channels
slack_get_channel_infoGet channel details
slack_get_channel_historyRead channel messages
slack_get_thread_repliesRead thread replies
slack_list_channel_membersList channel members
slack_search_messagesSearch messages
slack_get_reactionsGet message reactions
slack_list_reactionsList user's reactions
slack_list_starsList starred items
slack_get_user_infoGet user details
slack_list_usersList workspace members
slack_get_user_profileGet user profile
slack_list_filesList files (metadata only)
slack_get_file_infoGet file metadata
slack_send_messageSchedule a message SLACK_ADD_MESSAGE_DELAY ahead, or post it immediately when the delay is 0 (write)
slack_cancel_scheduled_messageCancel a scheduled message before it sends (write)

The two write tools need the chat:write scope in token mode.

Security

See SECURITY.md for the full security design document.

License

AGPL-3.0-or-later

Source: README.md at commit 7e2131d

Tools

0
SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

1
  1. v0.1.2LatestSep 16, 2026

Score

50% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 days25 pts

    Keep the endpoint answering the MCP handshake; SourceWeft probes it every 30 days.

  • Auth declared10 pts

    Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.

  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts