Slack MCP Server

npm install
npm run build

channels:read        # List channels
channels:history     # Read channel messages
groups:read          # List private channels
groups:history       # Read private channel messages
im:read              # List direct messages
im:history           # Read direct messages
mpim:read            # List group DMs
mpim:history         # Read group DMs
chat:write           # Send messages
users:read           # List users
users.profile:read   # Read user profiles
files:read           # List files
files:write          # Upload files
reactions:read       # Read reactions
reactions:write      # Add/remove reactions
search:read          # Search messages

https://your-platform.com/oauth/slack/callback

# Required
SLACK_ACCESS_TOKEN=xoxp-your-user-token

# Optional
SLACK_TEAM_ID=T0123456789

const SLACK_CLIENT_ID = 'your-client-id';
const REDIRECT_URI = 'https://your-platform.com/oauth/slack/callback';
const SCOPES = 'channels:read,channels:history,chat:write,users:read,files:read,files:write,reactions:read,reactions:write,search:read,groups:read,groups:history,im:read,im:history,mpim:read,mpim:history,users.profile:read';

const authUrl = `https://slack.com/oauth/v2/authorize?client_id=${SLACK_CLIENT_ID}&user_scope=${SCOPES}&redirect_uri=${encodeURIComponent(REDIRECT_URI)}&state=${generateRandomState()}`;

// Redirect user to authUrl

// In your callback handler
app.get('/oauth/slack/callback', async (req, res) => {
  const { code, state } = req.query;

  // Verify state to prevent CSRF
  if (!verifyState(state)) {
    return res.status(400).send('Invalid state');
  }

  // Exchange code for token
  const response = await fetch('https://slack.com/api/oauth.v2.access', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: new URLSearchParams({
      client_id: SLACK_CLIENT_ID,
      client_secret: SLACK_CLIENT_SECRET,
      code,
      redirect_uri: REDIRECT_URI,
    }),
  });

  const data = await response.json();

  if (data.ok) {
    // Save user token to your database
    const userToken = data.authed_user.access_token; // xoxp-...
    const userId = data.authed_user.id;
    const teamId = data.team.id;

    await db.saveSlackToken(currentUserId, {
      token: userToken,
      slackUserId: userId,
      teamId: teamId,
    });

    res.redirect('/success');
  } else {
    res.status(400).send(`OAuth error: ${data.error}`);
  }
});

// When starting the MCP server for a user, inject their token as env var
const userSlackToken = await db.getSlackToken(currentUserId);

const mcpProcess = spawn('node', ['/path/to/slack-mcp/dist/index.js'], {
  env: {
    ...process.env,
    SLACK_ACCESS_TOKEN: userSlackToken,
  },
});

{
  "mcpServers": {
    "slack": {
      "command": "node",
      "args": ["/path/to/slack-mcp/dist/index.js"],
      "env": {
        "SLACK_ACCESS_TOKEN": "xoxp-your-token"
      }
    }
  }
}

{
  "tool": "slack_list_channels",
  "arguments": {
    "types": "public_channel,private_channel",
    "limit": 50
  }
}

{
  "tool": "slack_send_message",
  "arguments": {
    "channel_id": "C1234567890",
    "text": "Hello from MCP!"
  }
}

{
  "tool": "slack_search_messages",
  "arguments": {
    "query": "from:@user in:#channel important",
    "count": 20
  }
}

{
  "error": "Slack API Error (invalid_auth): Invalid authentication token."
}