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mcp_slack_setup

Configure and authenticate the official Slack MCP server in Claude Code.

Updated Aug 5, 2026
Search Tags:#authentication#troubleshooting#oauth#claude code#configuration#mcp#slack
One-click install
npx skills add https://github.com/sayonari/claude-skills --skill mcp-slack-setup-sayonari
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: mcp_slack_setup
Source: https://github.com/sayonari/claude-skills/tree/main/mcp_slack_setup
Command: npx skills add https://github.com/sayonari/claude-skills --skill mcp-slack-setup-sayonari

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Adding Slack's official MCP server to Claude Code fails with the opaque error "SDK auth failed: Error from the MCP SDK" because Slack does not support dynamic client registration. This Skill diagnoses that root cause and walks through registering the server with the required OAuth client_id and callback_port. ## Core Features & Use Cases - Root-cause diagnosis: Identifies that a missing oauth key (clientId / callbackPort) in ~/.claude.json is why /mcp → Authenticate always fails. - Guided re-registration: Extracts a working clientId/callbackPort from an existing Slack MCP server and re-adds the server via claude mcp add --client-id --callback-port, including multi-workspace setups with the ?ws= parameter. - Use Case: You want to add a second Slack workspace's MCP server, but authentication stays stuck at "needs authentication". The Skill reuses the existing OAuth credentials, re-registers the server with the correct workspace subdomain, and instructs the user to verify the workspace shown in the browser authorization screen. ## Quick Start Fix my Slack MCP server in Claude Code that keeps failing authentication with an SDK auth failed error.

Frequently Asked Questions about mcp_slack_setup

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I fix "SDK auth failed" when authenticating the Slack MCP server in Claude Code?▼

The error occurs because Slack's MCP server does not support dynamic client registration, so the OAuth client_id and callback_port are missing. Re-register the server with claude mcp add --client-id <id> --callback-port <port> instead of adding it by URL alone.

How do I add a second Slack workspace MCP server to Claude Code?▼

Reuse the clientId and callbackPort from an already working Slack MCP server, since the same Slack app credentials apply across workspaces. Run claude mcp add with the new workspace subdomain in the ?ws= URL parameter.

Can I edit ~/.claude.json directly to add OAuth settings for an MCP server?▼

No, direct edits with Python or sed are discouraged because Claude Code may overwrite the file. Always use claude mcp remove and claude mcp add to change server configuration safely.

Why does Slack MCP authentication keep failing even after retrying Authenticate?▼

Repeatedly calling the authenticate tool returns the same SDK error because the underlying configuration lacks OAuth credentials. Retrying does not help; you must fix the client_id and callback_port configuration first, then restart Claude Code if the session holds stale settings.

How do I make sure I authorize the correct Slack workspace during MCP authentication?▼

Check the workspace shown in the top-right of the Slack authorization screen in the browser before approving. If you are logged into multiple workspaces, it is easy to accidentally authorize the wrong one.

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