Use Arialine from Slack's built-in assistant

Arialine exposes an MCP server at https://slack.arialine.app/mcp using Slack identity authentication. A Slack app administrator can register that URL in App Settings → MCP Servers with the Slack identity auth method.

Slack plan note: Slackbot is included on Slack Business+ (15 Slackbot messages per member per week) and Enterprise+; on Free and Pro it is available only during a trial or preview. Everything else in Arialine works on every Slack plan.

Slack's built-in assistant can then invoke Arialine tools to list boards, read history and decisions, create or edit diagrams, propose changes, undo, rewind, branch, export, and place a diagram on a Canvas. To explore alternatives, ask the assistant for options and have it apply the one you choose; for a rendered set of alternatives with Adopt and Branch buttons, ask @Arialine brainstorm in Slack.

MCP does not bypass Arialine's access rules or replace the native Slack app. It is another invocation surface for the same product capabilities, and only Slack-signed requests are accepted.

The assistant sees exactly what you can see. Every tool acts as the person asking. It lists, reads, searches and changes only boards in channels that person can open in Slack: members of a private channel, full workspace members for a public channel, and guests or Slack Connect partners only in channels they are in. A board in a channel you can't open behaves as if it doesn't exist. Creating a board needs access to the target channel.

How the assistant works with Arialine: the assistant writes the Mermaid itself; Arialine never rewrites it. To create a diagram, the assistant sends the complete Mermaid and a channel. To change one, it reads the current source, edits it, and sends the complete new diagram with a one-line summary of the change. Arialine checks the Mermaid before anything is saved. If it doesn't parse, or draws nothing, the assistant gets Mermaid's error message, fixes the diagram and tries again; nothing is created or changed in the meantime.

Edits follow the channel's setting: in a channel that applies edits directly, the new version is saved right away; in a channel that reviews edits, an Apply/Dismiss card appears in the board thread and Apply saves the assistant's diagram exactly as written. The assistant can also always ask for review instead. Undo through the assistant reverses the latest version; to remove an older change, ask it to edit the diagram, or to rewind to an earlier version.