MCP registry and docs generate broken setup command for Slack (missing clientId/OAuth config)

Summary

The Anthropic MCP registry API and the Claude Code MCP docs page list Slack with only a URL and no OAuth configuration. Following the generated command:

claude mcp add --transport http slack https://mcp.slack.com/mcp

results in:

Error: Incompatible auth server: does not support dynamic client registration

The command omits the required clientId, causing Claude Code to attempt RFC 7591 dynamic client registration, which Slack doesn't support.

What works

The official Slack docs say to use the plugin method:

claude plugin install slack

This bundles the correct OAuth config including the pre-registered clientId (1601185624273.8899143856786) and callbackPort (3118). Authentication completes successfully.

The manual config equivalent (from Slack's docs) is:

{
  "mcpServers": {
    "slack": {
      "type": "http",
      "url": "https://mcp.slack.com/mcp",
      "oauth": {
        "clientId": "1601185624273.8899143856786",
        "callbackPort": 3118
      }
    }
  }
}

The problem

Anthropic's own MCP registry and docs page point users to a claude mcp add command that is missing the required OAuth config. The working method (claude plugin install slack) is only documented on Slack's side. This is likely why many users are hitting authentication errors — they're following Anthropic's docs rather than Slack's.

Environment

• Claude Code v2.1.81
• Windows 11 Pro

Related

• #29934 — MCP OAuth fails with providers requiring HTTPS redirect URIs
• #38102 — MCP OAuth: "does not support dynamic client registration" despite clientId configured
• #3273 — Claude Code does not work with MCP servers that do not implement Dynamic Client Registration