Slack read-only workaround (skip official MCP)

June 28, 2026 · View on GitHub

When the goal is read recent DMs + channels without mcp.slack.com. Big picture: OAUTH_AND_HOSTING.md.

Official Slack MCP imposes: registered app, MCP toggle, public distribution / Marketplace, confidential OAuth. That’s built for Slack’s partner-scale remote MCP product—not for “let my agent read my threads.”

What you actually need

Goal	API	Token	Scopes (user token)
List DMs / channels joined	`conversations.list`	`xoxp-…` user token	`im:read`, `mpim:read`, `channels:read`, `groups:read`
Read recent messages	`conversations.history`	`xoxp-…`	`im:history`, `mpim:history`, `channels:history`, `groups:history`
Resolve names	`users.info`	`xoxp-…`	`users:read`
Post (optional)	`chat.postMessage`	`xoxp-…`	`chat:write`

Use a user token (xoxp-), not a bot token (xoxb-). Bots don’t see your DMs; they only see channels they’re invited to.

Workaround A — User token in Agent Deck vault (simplest today)

Best for: single workspace, read-first, you’re OK with “connect my Slack once.”

User creates an internal Slack app in their own workspace (no public distribution, no MCP toggle).
Add User Token Scopes only (read list above).
Install to workspace → copy User OAuth Token (xoxp-…).
Store in Agent Deck as a credential (same pattern as cred_slack / SLACK_BOT_TOKEN in playbooks—use user token instead).

Agent Deck (or a small connector) calls Slack Web API directly—no remote MCP.

Pros: No Marketplace, no Agent Deck shared secret, no mcp.slack.com policy.
Cons: User still creates a Slack app once (lighter than full MCP setup); paste token unless we add a short OAuth wizard for their app only.

Minimal manifest (read-only) — user: Create from manifest in their workspace:

{
  "display_information": { "name": "Agent Deck (read)" },
  "oauth_config": {
    "redirect_urls": ["http://localhost:8000/api/oauth/callback"],
    "scopes": {
      "user": [
        "channels:read",
        "channels:history",
        "groups:read",
        "groups:history",
        "im:read",
        "im:history",
        "mpim:read",
        "mpim:history",
        "users:read",
        "chat:write"
      ]
    }
  }
}

No bot_user, no MCP feature—internal app for one workspace only.

Workaround B — Local stdio Slack MCP + token

Best for: want MCP tools without mcp.slack.com.

Community servers (e.g. slack-messages, slack-mcp-server) take SLACK_USER_TOKEN / xoxp- in env.

Add as Agent Deck local-mcp service
Point env at vault credential
User still obtains xoxp- once (same as A)

Pros: MCP tool surface without Slack’s remote MCP gate.
Cons: Another package to run; token setup unchanged.

Workaround C — Official remote MCP (current preset)

Best for: parity with Cursor/Claude tool set, posting/canvases/search tools Slack ships on MCP.

Requires: SLACK_OAUTH_APP.md path (shared or BYO app + MCP enabled + distribution).

Keep this as the full path; don’t force it for read-only.

Workaround D — Host-only

Use Slack MCP only inside Cursor / Claude Code (partner apps). Agent Deck documents the deck; no Slack proxy.

Comparison

Path	Setup pain	Read DMs	Read joined channels	Non-technical UX
A User token + API	Medium (once per user)	✓	✓	Medium until guided OAuth
B Local MCP + token	Medium	✓	✓	Medium
C Official `mcp.slack.com`	High	✓	✓	Low unless hosted OAuth
D Cursor/Claude only	Low	✓	✓	High in host, none in Deck

Rate limit warning (read-heavy)

As of 2025, Slack tightened conversations.history for apps not on Marketplace / internal customer-built: about 1 request/minute, limit 15 messages per call. Read-heavy agents may need caching, search APIs, or Marketplace listing.

Plan for pagination + backoff if you build Workaround A/B.