slack-mcp

A lean MCP server that acts in Slack as you, through a user OAuth token (xoxp-…). One small Python process covers messaging, threads, search, users, channels, user groups and reactions, plus the APIs most Slack MCP servers skip: scheduled messages, canvases and Slack Lists.

Tools

Wherever a tool takes a channel, it accepts an ID, #channel-name, or @user for that user's DM. conversations_add_message and schedule_message also accept @a,@b for a group DM with those users (it needs the mpim:write scope; Slack returns the existing group DM when one exists). Only those two tools open a DM that does not exist yet; read tools fail instead. A user is matched by ID, handle, then display or real name, and an ambiguous name is refused. Paging cursors carry the original window and page size. Tool names and parameters match korotovsky/slack-mcp-server for the overlapping tools, so existing prompts and permission rules keep working.

Related MCP server: Slack MCP Server

Setup

1. Create a Slack app at https://api.slack.com/apps → From a manifest:

   {
     "display_information": { "name": "Slack MCP" },
     "oauth_config": {
       "scopes": {
         "user": [
           "channels:history", "channels:read", "groups:history", "groups:read",
           "im:history", "im:read", "im:write", "mpim:history", "mpim:read", "mpim:write",
           "users:read", "users:read.email", "chat:write", "search:read",
           "usergroups:read", "reactions:write",
           "canvases:read", "canvases:write", "files:read", "files:write", "lists:read", "lists:write"
         ]
       }
     },
     "settings": { "org_deploy_enabled": false, "socket_mode_enabled": false, "token_rotation_enabled": false }
   }

   Drop the scopes for tools you will not use; a call that needs a missing scope fails with missing_scope (token lacks scope: …).

2. Install to Workspace and copy the User OAuth Token.

3. Register a launcher that reads the token from your secret manager at startup, so the token never lands in a config file or on a command line:

   #!/usr/bin/env bash
   # slack-mcp-start.sh
   SLACK_USER_TOKEN="$(op read 'op://Private/Slack MCP/token')" || exit 1   # or any secret manager
   export SLACK_USER_TOKEN
   exec uvx --from git+https://github.com/asaphe/slack-mcp slack-mcp

   claude mcp add slack --scope user -- /path/to/slack-mcp-start.sh

   Avoid claude mcp add … -e SLACK_USER_TOKEN="$(…)": the shell expands the secret before Claude Code runs, and it is stored in plain text in ~/.claude.json.

Security

• The token is read from SLACK_USER_TOKEN only, sent only in the Authorization header to slack.com/api/ and, for canvas_read, to files.slack.com over HTTPS (any other file URL is refused and redirects are not followed). It is never logged or included in errors.

• Posting tools act as you. Gate them in your MCP client (for Claude Code: permissions.ask on mcp__slack__conversations_add_message, schedule_message, canvas_create, canvas_edit, list_create, list_item_create, list_items_update, delete_scheduled_message, reactions_*).

• No telemetry, no disk cache; user and channel directories live in memory for the process lifetime.

• Tools run in worker threads, so a slow Slack call or a rate-limit wait never blocks the MCP connection.

Development

uv sync --all-groups
uv run pytest
uv run ruff check . && uv run ruff format --check . && uv run mypy src

License

MIT