Slack (archived)
Slack MCP was Anthropic's reference server for reading channels and posting messages in a Slack workspace over the Model Context Protocol, published as @modelcontextprotocol/server-slack on npm. It is archived: npm prints a deprecation notice saying the package is no longer supported. The code still installs and still runs, but nobody is maintaining it against a live Slack API.
How we started it
npx -y @modelcontextprotocol/server-slackSkip it unless you already have a Slack app and enjoy pinning a dead dependency. It did not boot for us, because our probe runs with a clean env and the server wants a bot token and a team ID before it will speak protocol at all, which is correct behaviour for a Slack client and useless for anyone hoping to try it first. Give it credentials and it will presumably work as it always did. The reason against is not the token dance, it is the deprecation line npm prints at you: an unmaintained bridge to an API that changes on someone else's schedule.
Use it if
Skip it if
The bill for your context window
There is no context tax to report here, and that absence is the finding. Because the server refuses to complete initialize without credentials, our clean-env probe never received a tools/list payload, so the recorded token estimate is zero rather than small, and zero here means unknown. Every other page in this batch can tell you which tools carry the weight; this one cannot name a single tool it exposes. A Slack client with a handful of read and post calls would sit at the light end of what we have measured elsewhere, but a guess is not a measurement and we are not going to print one as if it were.
Setup reality
We started it exactly the way the README suggests, npx against @modelcontextprotocol/server-slack, with no secrets in the environment. It exited with code 1 before initialize completed and told us plainly on stderr to set SLACK_BOT_TOKEN and SLACK_TEAM_ID (measured 2026-08-19). That is the whole gate, and it is a fail-fast check rather than a crash. The real work happens outside the process: create a Slack app, add the scopes for the channels and history you want, install it to the workspace, copy the bot token, and find your team ID. Transport is stdio. The npm deprecation warning arrives before any of that, on every install.
SLACK_BOT_TOKENSLACK_TEAM_IDQuestions people ask
Is the Slack MCP server still maintained?
No. Installing it prints an npm deprecation notice saying the package is no longer supported, and the reference server was archived. It runs, but no one is tracking Slack API changes on your behalf.
Why did it exit immediately when I ran it?
It checks for SLACK_BOT_TOKEN and SLACK_TEAM_ID at startup and exits before completing initialize if either is missing. That is what happened on our clean-env run, with exit code 1 and a one-line message on stderr.
How many tools does it expose and what do they cost in context?
We cannot tell you from measurement. Without credentials the server never answered tools/list, so we recorded no tool count and no token estimate. Any number you see elsewhere came from someone running it with a live workspace token.
What should I use instead?
Look at the maintained community Slack MCP servers, or wire Slack's Web API directly if your agent only needs to post. Either way you end up managing the same bot token and scopes, so the choice is really about who patches the client.
How this page is made: the server is spawned as an unprivileged user with a clean environment and no credentials, then asked for its tools, resources and prompts over stdio. Token figures are estimates at four characters per token, not a tokenizer count. One run, one machine. Corrections: contact the desk.