Merge pull request modelcontextprotocol#28 from modelcontextprotocol/justin/sampling

Add tab and approval flow for server -> client sampling

Author: jspahrsummers

client/src/App.tsx

@@ -1,18 +1,10 @@
-import { Button } from "@/components/ui/button";
-import { Input } from "@/components/ui/input";
-import {
-  Select,
-  SelectContent,
-  SelectItem,
-  SelectTrigger,
-  SelectValue,
-} from "@/components/ui/select";
-import { Tabs, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { SSEClientTransport } from "@modelcontextprotocol/sdk/client/sse.js";
 import {
   CallToolResultSchema,
   ClientRequest,
+  CreateMessageRequestSchema,
+  CreateMessageResult,
   EmptyResultSchema,
   GetPromptResultSchema,
   ListPromptsResultSchema,
@@ -24,16 +16,28 @@ import {
   ServerNotification,
   Tool,
 } from "@modelcontextprotocol/sdk/types.js";
+import { useEffect, useRef, useState } from "react";
+
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from "@/components/ui/select";
+import { Tabs, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import {
   Bell,
   Files,
   Hammer,
+  Hash,
   MessageSquare,
   Play,
   Send,
   Terminal,
 } from "lucide-react";
-import { useEffect, useRef, useState } from "react";
 
 import { AnyZodObject } from "zod";
 import "./App.css";
@@ -43,6 +47,7 @@ import PingTab from "./components/PingTab";
 import PromptsTab, { Prompt } from "./components/PromptsTab";
 import RequestsTab from "./components/RequestsTabs";
 import ResourcesTab from "./components/ResourcesTab";
+import SamplingTab, { PendingRequest } from "./components/SamplingTab";
 import Sidebar from "./components/Sidebar";
 import ToolsTab from "./components/ToolsTab";
 
@@ -77,6 +82,32 @@ const App = () => {
   const [mcpClient, setMcpClient] = useState<Client | null>(null);
   const [notifications, setNotifications] = useState<ServerNotification[]>([]);
 
+  const [pendingSampleRequests, setPendingSampleRequests] = useState<
+    Array<
+      PendingRequest & {
+        resolve: (result: CreateMessageResult) => void;
+        reject: (error: Error) => void;
+      }
+    >
+  >([]);
+  const nextRequestId = useRef(0);
+
+  const handleApproveSampling = (id: number, result: CreateMessageResult) => {
+    setPendingSampleRequests((prev) => {
+      const request = prev.find((r) => r.id === id);
+      request?.resolve(result);
+      return prev.filter((r) => r.id !== id);
+    });
+  };
+
+  const handleRejectSampling = (id: number) => {
+    setPendingSampleRequests((prev) => {
+      const request = prev.find((r) => r.id === id);
+      request?.reject(new Error("Sampling request rejected"));
+      return prev.filter((r) => r.id !== id);
+    });
+  };
+
   const [selectedResource, setSelectedResource] = useState<Resource | null>(
     null,
   );
@@ -229,6 +260,15 @@ const App = () => {
         },
       );
 
+      client.setRequestHandler(CreateMessageRequestSchema, (request) => {
+        return new Promise<CreateMessageResult>((resolve, reject) => {
+          setPendingSampleRequests((prev) => [
+            ...prev,
+            { id: nextRequestId.current++, request, resolve, reject },
+          ]);
+        });
+      });
+
       setMcpClient(client);
       setConnectionStatus("connected");
     } catch (e) {
@@ -314,6 +354,15 @@ const App = () => {
                     <Bell className="w-4 h-4 mr-2" />
                     Ping
                   </TabsTrigger>
+                  <TabsTrigger value="sampling" className="relative">
+                    <Hash className="w-4 h-4 mr-2" />
+                    Sampling
+                    {pendingSampleRequests.length > 0 && (
+                      <span className="absolute -top-1 -right-1 bg-red-500 text-white text-xs rounded-full h-4 w-4 flex items-center justify-center">
+                        {pendingSampleRequests.length}
+                      </span>
+                    )}
+                  </TabsTrigger>
                 </TabsList>
 
                 <div className="w-full">
@@ -362,6 +411,11 @@ const App = () => {
                       );
                     }}
                   />
+                  <SamplingTab
+                    pendingRequests={pendingSampleRequests}
+                    onApprove={handleApproveSampling}
+                    onReject={handleRejectSampling}
+                  />
                 </div>
               </Tabs>
             ) : (

client/src/components/SamplingTab.tsx

@@ -0,0 +1,65 @@
+import { Alert, AlertDescription } from "@/components/ui/alert";
+import { Button } from "@/components/ui/button";
+import { TabsContent } from "@/components/ui/tabs";
+import {
+  CreateMessageRequest,
+  CreateMessageResult,
+} from "@modelcontextprotocol/sdk/types.js";
+
+export type PendingRequest = {
+  id: number;
+  request: CreateMessageRequest;
+};
+
+export type Props = {
+  pendingRequests: PendingRequest[];
+  onApprove: (id: number, result: CreateMessageResult) => void;
+  onReject: (id: number) => void;
+};
+
+const SamplingTab = ({ pendingRequests, onApprove, onReject }: Props) => {
+  const handleApprove = (id: number) => {
+    // For now, just return a stub response
+    onApprove(id, {
+      model: "stub-model",
+      stopReason: "endTurn",
+      role: "assistant",
+      content: {
+        type: "text",
+        text: "This is a stub response.",
+      },
+    });
+  };
+
+  return (
+    <TabsContent value="sampling" className="h-96">
+      <Alert>
+        <AlertDescription>
+          When the server requests LLM sampling, requests will appear here for
+          approval.
+        </AlertDescription>
+      </Alert>
+      <div className="mt-4 space-y-4">
+        <h3 className="text-lg font-semibold">Recent Requests</h3>
+        {pendingRequests.map((request) => (
+          <div key={request.id} className="p-4 border rounded-lg space-y-4">
+            <pre className="bg-gray-50 p-2 rounded">
+              {JSON.stringify(request.request, null, 2)}
+            </pre>
+            <div className="flex space-x-2">
+              <Button onClick={() => handleApprove(request.id)}>Approve</Button>
+              <Button variant="outline" onClick={() => onReject(request.id)}>
+                Reject
+              </Button>
+            </div>
+          </div>
+        ))}
+        {pendingRequests.length === 0 && (
+          <p className="text-gray-500">No pending requests</p>
+        )}
+      </div>
+    </TabsContent>
+  );
+};
+
+export default SamplingTab;