Connect Claude Code to Slack MCP through a custom Slack app

[bigunyak]

Hello,

Is it possible to configure a custom MySlack app (not Claude app) to connect from ClaudeCode to Slack MCP?
I was trying configuring my own app and then using that app's clientId in the MCP configuration like below:

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

The error I get back says "redirect_uri did not match any configured URIs. Passed URI: http://localhost:3118/callback".
But when I try registering http://localhost:3118/callback in my app's configuration, I'm not able to do it because of Please use a complete URL beginning with https (for security) error which blocks registering http redirects.

Can someone explain if it's even possible and how to do it correctly?

[mwbrooks]

Hi @bigunyak 👋🏻 Thanks for trying out the Slack MCP Server 🙇🏻

Here is a sample app that demonstrates how to use the Slack MCP Server in a custom Slack App:
https://github.com/slack-samples/bolt-js-slack-mcp-server

The error I get back says "redirect_uri did not match any configured URIs. Passed URI: http://localhost:3118/callback".
But when I try registering http://localhost:3118/callback in my app's configuration, I'm not able to do it because of Please use a complete URL beginning with https (for security) error which blocks registering http redirects.

Can someone explain if it's even possible and how to do it correctly?

The Slack MCP Server requires a User Token (xoxp). This is always a painful spot for local development, but we're actively working to make this easier for developers.

In the meantime, please see the OAuth Section of the Sample App for an explaination of how to use ngrok to setup a local tunnel between a public HTTPS URL and your local machine:
https://github.com/slack-samples/bolt-js-slack-mcp-server?tab=readme-ov-file#oauth

Let me know how that goes!

[bigunyak]

@mwbrooks thanks for the example, but this is not quite how I thought the process should work.
My impression was that I only need to create an app under https://api.slack.com/apps, assign desired permissions and then use that app as a gateway to access Slack MCP. Why would I need any JS code installed?