Slack MCP server

Connect Slack's hosted MCP server through the LiteLLM MCP Gateway for workspace search, channel reads, and messaging.

Slack hosts and maintains the server, so there is nothing to deploy or run yourself. LiteLLM adds centralized auth, access control by key and team, cost tracking per tool call, and one audit trail across every MCP server you expose.

When should you use this server

Give an agent workspace context: what was decided in a channel, who said it, and when
Let an agent post updates, summaries, or alerts into Slack instead of only reporting back in chat
Search across messages, files, and canvases as a retrieval step before answering

Key features

Tool surface depends on the OAuth scopes you grant, so a read-only rollout and a full read/write rollout use the same server with different consent
Hosted by Slack over Streamable HTTP; no local process, no bot token to rotate
Per-user auth, so every tool call runs as the signed-in person and only sees what they can already see in Slack

Authentication

Method: OAuth 2.1 with user tokens. Slack does not support dynamic client registration, so you create a Slack app and give LiteLLM its client credentials.
Slack app: Create one at api.slack.com/apps. You will set a redirect URL, add user token scopes, and enable the Model Context Protocol toggle. Slack only permits MCP on internal apps and directory-published apps, so an app built in your own workspace qualifies.

Endpoint

Remote MCP server:

https://mcp.slack.com/mcp

Connect via LiteLLM MCP Gateway

info

Slack is one of the servers that needs explicit client credentials. LiteLLM normally handles OAuth client setup for you through dynamic registration, as on the Atlassian and Linear servers, but Slack requires your own app.

Step 1: Create a Slack OAuth app

Go to api.slack.com/apps, click Create New App, then From scratch, and pick the workspace agents should reach.
Open OAuth & Permissions.
Under Redirect URLs, add {PROXY_BASE_URL}/callback and click Save URLs:
```
https://llm.example.com/callback
```
Replace https://llm.example.com with the origin users see in their address bar. This is the value LiteLLM sends upstream as the redirect_uri, so a mismatch fails the flow at Slack's consent screen. See Reverse proxy and ingress configuration if LiteLLM sits behind an ingress.
Under User Token Scopes, add the scopes for the capabilities you want, matching the table in Tools provided. Start read-only for a broad rollout and add write scopes for teams you trust.
From Basic Information, copy the Client ID and Client Secret.

Step 2: Enable MCP (Agents & AI Apps)

warning

The MCP endpoint sits behind a per-app toggle under Agents & AI Apps. If you leave it off, OAuth still succeeds and the tool list comes back empty or 403, which reads like a LiteLLM permissions problem when it is not.

In the app settings, open Agents & AI Apps.
Enable Model Context Protocol.
Install or reinstall the app to the workspace so the new scopes take effect.

Step 3: Register the server in LiteLLM

LiteLLM UI
config.yaml

Navigate to MCP Servers, click + Add New MCP Server, and set:

Field	Value
Server Name	`slack_mcp`
Transport	HTTP
Server URL	`https://mcp.slack.com/mcp`
Authentication	OAuth
OAuth flow type	Interactive (PKCE)
Client ID / Client Secret	From Step 1

Click Create MCP Server, then open the server's MCP Tools tab to confirm LiteLLM can list Slack's tools. The first listing triggers the browser sign-in.

config.yaml
mcp_servers:
  slack_mcp:
    url: "https://mcp.slack.com/mcp"
    transport: "http"
    description: "Slack workspace search, channels, and messaging"
    auth_type: oauth2
    oauth2_flow: authorization_code
    client_id: os.environ/SLACK_OAUTH_CLIENT_ID
    client_secret: os.environ/SLACK_OAUTH_CLIENT_SECRET

oauth2_flow: authorization_code selects the interactive per-user flow and is required; the proxy refuses to start on an auth_type: oauth2 server that omits it. Storing MCP servers also needs store_model_in_db: true, covered in Prerequisites.

Step 4: Connect from an agent

The gateway serves each server at http://localhost:4000/{server_name}/mcp, so slack_mcp is reachable at http://localhost:4000/slack_mcp/mcp.

Claude Desktop / Cursor
Claude Code

Claude Desktop / Cursor
{
  "mcpServers": {
    "slack": {
      "url": "http://localhost:4000/slack_mcp/mcp",
      "headers": {
        "x-litellm-api-key": "Bearer $LITELLM_API_KEY"
      }
    }
  }
}

claude mcp add --transport http slack http://localhost:4000/slack_mcp/mcp \
  --header "x-litellm-api-key: Bearer $LITELLM_API_KEY"

The first call opens a browser for Slack sign-in. LiteLLM stores that user's token and refreshes it afterwards, so subsequent sessions connect without prompting.

Tools provided

info

Slack publishes its tool definitions at runtime through tools/list, so names and fields can change without notice. The MCP Tools tab in the LiteLLM UI is the source of truth for what your workspace exposes; it lists the live tools and lets you call one with test arguments. See Slack's Slack MCP server overview for upstream detail.

Area	Tools
Search	`search_public`, `search_public_and_private`, `search_channels`, `search_users`
Read	`read_channel`, `read_thread`, `read_user_profile`
Messaging	`send_message`, `send_message_draft`, `schedule_message`
Canvases	`create_canvas`, `read_canvas`, `update_canvas`

Canvas tools require a paid Slack plan. LiteLLM prefixes tool names with the server name, so search_public is exposed to models as slack_mcp-search_public; see Tool naming.

OAuth scopes by capability

Capability	User token scopes (examples)
Search messages and files	`search:read`
Read public channels	`channels:read`, `channels:history`
Read private channels	`groups:read`, `groups:history`
Read direct messages	`im:history`
Post messages	`chat:write`
Resolve user profiles	`users:read`
Read files	`files:read`

Slack documents the full list in OAuth scopes. Rate limits are applied per tool, matching the tier of the equivalent Web API method, and stack on top of anything you configure in LiteLLM.

Restrict who can use it

Grant the server per key or per team with object_permission, and cap call volume per server with mcp_rpm_limit, both covered in MCP Permission Management. Grant the narrowest scope set that works for the audience; a key that only needs to summarize channels does not need chat:write.

Put the LiteLLM key in x-litellm-api-key

Interactive OAuth needs the Authorization header free for the upstream token. If a client sends the LiteLLM API key as Authorization: Bearer sk-..., the OAuth flow never runs and LiteLLM forwards your LiteLLM key to Slack, which rejects it. To diagnose, add x-litellm-mcp-debug: true and read the response headers: SAME_AS_LITELLM_KEY confirms this case, and m2m-client-credentials means a token_url is set and every caller shares one identity. See Debugging OAuth and the MCP Troubleshooting Guide.

When should you use this server​

Key features​

Authentication​

Endpoint​

Connect via LiteLLM MCP Gateway​

Step 1: Create a Slack OAuth app​

Step 2: Enable MCP (Agents & AI Apps)​

Step 3: Register the server in LiteLLM​

Step 4: Connect from an agent​

Tools provided​

OAuth scopes by capability​