Is Mattermost's server for self-hosted instances?

Yes. It connects assistants to a self-hosted Mattermost workspace, which suits teams running the open-source platform on their own infrastructure.

Does the Slack server need a bot installed?

No. It can run without installing a workspace bot — stealth mode uses browser session tokens and OAuth mode uses a user or bot token — which is helpful when you cannot add a bot.

Mattermost vs Slack

Both of these maintained community MCP servers connect an agent to a team-chat workspace, but one targets a self-hosted, open-source platform and the other targets Slack with a clever no-bot connection model. The Mattermost server (cloud.ru) connects assistants to a self-hosted Mattermost workspace and exposes the things a chat agent actually needs: listing public and personal channels, creating and joining channels, opening direct channels, posting and editing messages, searching messages and users, and working with threads, reactions, teams, and files. The Slack server (korotovsky) stands out because it can run without installing a workspace bot — stealth mode uses browser session tokens, OAuth mode uses a user or bot token — then reads conversation history and threads, searches messages, posts, adds reactions, and lists channels. So the choice tracks whether your team is on self-hosted Mattermost or on Slack, plus each server's connection model. Here is how they compare for an agent.

How they compare

Dimension	Mattermost	Slack
Platform	Self-hosted, open-source Mattermost — you run the server and the agent connects to your instance.	Slack — the hosted team-chat SaaS, reached without installing a workspace bot.
Connection model	Connects to a Mattermost workspace with credentials/token against your instance.	No bot install required: stealth mode via browser session tokens, OAuth mode via user or bot token.
Channel management	Create, join, and leave channels, open direct channels, and mark channels viewed.	Join and leave conversations and list channels; centered on reading and posting.
Common surface	Post and edit messages, search messages and users, and handle threads, reactions, teams, and files.	History and replies, message search, posting, reactions, and channel listing across the workspace.
Best-fit task	Wiring an agent into a self-hosted Mattermost deployment for full team-chat operations.	Adding an agent to a Slack workspace's history, search, and posting without admin bot setup.

Verdict

Choose by the platform your team runs. The Mattermost server is the pick when your chat lives on self-hosted, open-source Mattermost and you want full team-chat operations — creating and joining channels, posting and editing, searching, and handling threads, reactions, teams, and files against your own instance. The Slack server is the choice for Slack workspaces, and its standout is the no-bot connection: read history and threads, search, post, and react using session or OAuth tokens, which avoids workspace bot install. Both are capable community servers, so the real decision is Mattermost-self-hosted versus Slack-SaaS, with the Slack server's frictionless connection a notable plus. Match the server to where your team actually chats.

FAQ

Is Mattermost's server for self-hosted instances?: Yes. It connects assistants to a self-hosted Mattermost workspace, which suits teams running the open-source platform on their own infrastructure.
Does the Slack server need a bot installed?: No. It can run without installing a workspace bot — stealth mode uses browser session tokens and OAuth mode uses a user or bot token — which is helpful when you cannot add a bot.