Crush

Crush takes Grounder as an HTTP server in crush.json (or ~/.config/crush/crush.json) and offers sign-in in its interface.

{
  "mcp": {
    "grounder": {
      "type": "http",
      "url": "https://api.grounder.net/mcp",
      "oauth": true
    }
  }
}
// sign in from Crush's interface

"oauth": true is what makes Crush offer sign-in; it has no mcp command.