diff --git a/package-lock.json b/package-lock.json
index aacc3f3a5..6e1f829cf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@tableau/mcp-server",
-  "version": "2.6.3",
+  "version": "2.6.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@tableau/mcp-server",
-      "version": "2.6.3",
+      "version": "2.6.4",
       "license": "Apache-2.0",
       "dependencies": {
         "@modelcontextprotocol/ext-apps": "^1.7.2",
diff --git a/package.json b/package.json
index 9c0f6422e..0fd410a7c 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@tableau/mcp-server",
   "description": "Helping agents see and understand data.",
-  "version": "2.6.3",
+  "version": "2.6.4",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/tableau/tableau-mcp.git"
diff --git a/src/server/oauth/authMiddleware.ts b/src/server/oauth/authMiddleware.ts
index d4cbacbbc..8577558e3 100644
--- a/src/server/oauth/authMiddleware.ts
+++ b/src/server/oauth/authMiddleware.ts
@@ -130,7 +130,8 @@ export function authMiddleware(accessTokenValidator: AccessTokenValidator): Requ
           ...(shouldCheckApiScopes ? requiredApiScopes : []),
         ];
         const scopeParam = `scope="${formatScopes(requiredScopesForChallenge)}"`;
-        const wwwAuthenticate = `Bearer realm="MCP", error="insufficient_scope", error_description="Missing required scopes", resource_metadata="${resourceMetadataUrl}", ${scopeParam}`;
+        const errorDescription = `Missing required scopes: ${formatScopes(missingScopes)}`;
+        const wwwAuthenticate = `Bearer realm="MCP", error="insufficient_scope", error_description="${errorDescription}", resource_metadata="${resourceMetadataUrl}", ${scopeParam}`;
 
         if (req.method === 'GET' && req.headers.accept?.includes('text/event-stream')) {
           res.writeHead(403, {
@@ -141,7 +142,7 @@ export function authMiddleware(accessTokenValidator: AccessTokenValidator): Requ
           });
           res.write('event: error\n');
           res.write(
-            'data: {"error": "insufficient_scope", "error_description": "Missing required scopes"}\n\n',
+            `data: ${JSON.stringify({ error: 'insufficient_scope', error_description: errorDescription })}\n\n`,
           );
           res.end();
           return;
@@ -149,7 +150,7 @@ export function authMiddleware(accessTokenValidator: AccessTokenValidator): Requ
 
         res.status(403).header('WWW-Authenticate', wwwAuthenticate).json({
           error: 'insufficient_scope',
-          error_description: 'Missing required scopes',
+          error_description: errorDescription,
         });
         return;
       }