slack-mcp-server

name	slack-mcp-server
description	MCP server enabling Claude Code to send messages, read channels, manage threads, and search Slack workspaces with HITL approval for external communications. Use when Claude needs Slack integration for team communication, notifications, or workflow automation.

Slack MCP Server

Overview

The Slack MCP Server is a Model Context Protocol (MCP) server built with FastMCP that enables Claude Code to interact with Slack workspaces. It provides secure, human-monitored access to Slack functionality with Human-in-the-Loop (HITL) enforcement for sensitive operations such as messaging external channels, sending DMs to new users, file uploads, and bulk messaging.

Prerequisites

Slack Bot Token

1. Create a Slack App at https://api.slack.com/apps
2. Navigate to OAuth & Permissions
3. Add the following Bot Token Scopes:

Scope	Purpose
channels:read	List and get info about public channels
channels:history	Read messages in public channels
groups:read	List and get info about private channels
groups:history	Read messages in private channels
chat:write	Send messages as the bot
files:write	Upload files
files:read	Read file metadata
reactions:write	Add emoji reactions
reactions:read	Read emoji reactions
search:read	Search messages in the workspace
users:read	Read user profiles
im:history	Read DM history
im:write	Open DM channels

4. Install the app to your workspace
5. Copy the Bot User OAuth Token (starts with xoxb-)

Environment Variables

SLACK_BOT_TOKEN=xoxb-your-bot-token
SLACK_APP_TOKEN=xapp-your-app-token        # Optional: for Socket Mode
SLACK_DEFAULT_CHANNEL=general               # Optional: default channel
SLACK_SIGNING_SECRET=your-signing-secret    # Optional: for request verification

Quick Start

# Install dependencies
pip install -r .claude/skills/slack-mcp-server/assets/requirements.txt

# Set environment variable
export SLACK_BOT_TOKEN=xoxb-your-bot-token

# Run the server
python .claude/skills/slack-mcp-server/scripts/slack_mcp_server.py

MCP Tools

Available Operations

Tool	Description	HITL Required
send_message	Send a message to a channel or thread	External channels only
read_channel	Read recent messages from a channel	No
search_messages	Search messages across the workspace	No
list_channels	List channels in the workspace	No
get_channel_info	Get detailed channel information	No
upload_file	Upload a file to a channel	Always
add_reaction	Add an emoji reaction to a message	No
get_thread	Get all replies in a thread	No

Python Usage

from slack_mcp_server import create_slack_mcp_server

# Create and run the server
server = create_slack_mcp_server()
server.run()

Tool Examples

# Send a message
await send_message(channel="#general", text="Hello from Claude!")

# Send a threaded reply
await send_message(channel="#general", text="Reply here", thread_ts="1234567890.123456")

# Read last 10 messages
messages = await read_channel(channel="#general", limit=10)

# Search workspace
results = await search_messages(query="deployment update", count=5)

# Upload a file
await upload_file(channel="#general", content="Report data...", filename="report.txt", title="Daily Report")

# Add a reaction
await add_reaction(channel="#general", timestamp="1234567890.123456", emoji="thumbsup")

# Get thread replies
thread = await get_thread(channel="#general", thread_ts="1234567890.123456")

HITL Controls

Approval Matrix

Action	Condition	HITL Required
Send message	Internal channel	No
Send message	External/shared channel	Yes
Send DM	Previously messaged user	No
Send DM	New user (first contact)	Yes
Upload file	Any channel	Yes
Bulk messages	More than 3 in 60 seconds	Yes
Add reaction	Any message	No
Read channel	Any channel	No
Search messages	Any query	No

Approval Workflow

1. Claude requests a HITL-gated operation
2. An approval request is written to Pending_Approval/ directory
3. Human reviews and approves or rejects via the approval file
4. On approval, the operation executes and result is returned
5. All decisions are audit-logged

Configuration

config_manager.py Settings

@dataclass
class SlackConfig:
    bot_token: str              # SLACK_BOT_TOKEN
    app_token: str              # SLACK_APP_TOKEN (optional)
    default_channel: str        # Default channel for messages
    hitl_enabled: bool          # Enable/disable HITL globally
    hitl_external_channels: bool # Require approval for external channels
    hitl_new_dm_users: bool     # Require approval for new DM recipients
    hitl_file_uploads: bool     # Require approval for file uploads
    hitl_bulk_threshold: int    # Message count triggering bulk HITL
    hitl_bulk_window_seconds: int # Window for counting bulk messages
    rate_limit_per_minute: int  # Max API calls per minute
    rate_limit_per_second: int  # Max API calls per second
    audit_log_path: str         # Path to audit log file
    approval_dir: str           # Directory for pending approvals
    approval_timeout_seconds: int # How long approvals remain valid

Rate Limiting

The server enforces Slack API rate limits:

• Tier 1: 1 request per second (most write operations)
• Tier 2: 20 requests per minute (search, list operations)
• Tier 3: 50 requests per minute (read operations)

Custom rate limits can be configured via SlackConfig.

Architecture

slack_mcp_server.py      -- FastMCP server with 8 tool endpoints
approval_workflow.py     -- HITL approval engine with file-based workflow
config_manager.py        -- Configuration dataclass and environment loader

Security Considerations

• Bot tokens are loaded from environment variables, never hardcoded
• All write operations are audit-logged with timestamps and context
• HITL approval is enforced for sensitive operations before execution
• Rate limiting prevents accidental API abuse
• File uploads always require human approval regardless of destination
• The approval directory should have restricted filesystem permissions

Resources

scripts/

Python scripts for the FastMCP server, HITL approval workflow, and configuration management.

assets/

Requirements file and configuration templates.

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The Slack MCP server enables secure and compliant Slack workspace operations with appropriate human oversight.