web-slack-mcp

An MCP server that reads Slack through the web app, driven by Playwright over your own logged-in browser session.

Built for the case where you're a guest in a workspace and can't install a Slack app or mint API tokens — so instead of an app, it reuses the session in a persistent Chromium profile that you log into once.

Draft-only by design. It reads channels, messages, and threads, and (later) stages replies in the composer. There is no send code path in this server — it never posts a message.

How it works

• Login is manual and one-time: a visible Chromium window opens, you sign in (SSO / magic link / whatever your workspace uses), and the session is saved to a persistent profile so it survives restarts.
• Reads go through Slack's own internal JSON API (conversations.history, conversations.replies, conversations.view), replayed from inside the logged-in browser context so the session cookie + boot token authenticate them. This is far more robust than scraping the virtualized React DOM.
• Navigation uses the UI only to resolve a human channel name to its id (the quick switcher routes to /client/T…/<channel id>, which we read off the URL).
• Names — including Slack Connect / external members that per-id lookups won't return — are harvested in one conversations.view call per channel.

Tools

Tool	Description
list_channels	List channels/DMs visible in your sidebar.
read_messages	Read recent messages in a channel/DM (channel, limit).
read_thread	Read a thread by matching text in its parent message.
search_messages	Search messages workspace-wide with Slack search syntax.

Requirements

• Python 3.13+
• uv (provides uvx)

Install & run

Run straight from GitHub with uvx — no clone needed:

uvx --from git+https://github.com/sercant/web-slack-mcp web-slack-mcp

On the first launch the server downloads the Chromium build Playwright drives into Playwright's shared cache (~/Library/Caches/ms-playwright on macOS), so it happens once and persists across runs.

Register with Claude Code

claude mcp add web-slack -- \
  uvx --from git+https://github.com/sercant/web-slack-mcp web-slack-mcp

Then reload Claude Code; the tools appear as mcp__web-slack__*. The first time you call a read tool while signed out, the server opens a visible Chromium and waits for you to sign in — no separate step. The session is saved and reused on later runs.

Other MCP clients

Any client that speaks stdio works — point it at the same command:

{
  "mcpServers": {
    "web-slack": {
      "command": "uvx",
      "args": [
        "--from", "git+https://github.com/sercant/web-slack-mcp",
        "web-slack-mcp"
      ]
    }
  }
}

Configuration

All optional, via environment variables:

Variable	Default	Purpose
SLACK_URL	https://app.slack.com/client	Slack web client URL.
SLACK_PROFILE_DIR	.slack-profile	Where the persistent browser profile (your session) lives.
SLACK_HEADLESS	0	1 runs headless. Login needs a visible window, so keep 0 for the initial sign-in.
SLACK_LOGIN_WAIT	180	Seconds a read tool waits for you to finish signing in before giving up.

The profile directory holds your live Slack session — treat it like a credential and keep it out of version control (it's gitignored here).

Local development

git clone https://github.com/sercant/web-slack-mcp
cd web-slack-mcp
uv sync
uv run web-slack-mcp

License

MIT