Add support for MCP server instructions behind config option (#13432)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/core/src/tools/mcp-client-manager.ts

@@ -323,4 +323,20 @@ export class McpClientManager {
     }
     return mcpServers;
   }
+
+  getMcpInstructions(): string {
+    const instructions: string[] = [];
+    for (const [name, client] of this.clients) {
+      // Only include instructions if explicitly enabled in config
+      if (client.getServerConfig().useInstructions) {
+        const clientInstructions = client.getInstructions();
+        if (clientInstructions) {
+          instructions.push(
+            `# Instructions for MCP Server '${name}'\n${clientInstructions}`,
+          );
+        }
+      }
+    }
+    return instructions.join('\n\n');
+  }
 }