diff --git a/client/src/components/JsonView.tsx b/client/src/components/JsonView.tsx
index 9787b76..3fcbf8e 100644
--- a/client/src/components/JsonView.tsx
+++ b/client/src/components/JsonView.tsx
@@ -12,6 +12,7 @@ interface JsonViewProps {
   initialExpandDepth?: number;
   className?: string;
   withCopyButton?: boolean;
+  isError?: boolean;
 }
 
 const JsonView = memo(
@@ -21,6 +22,7 @@ const JsonView = memo(
     initialExpandDepth = 3,
     className,
     withCopyButton = true,
+    isError = false,
   }: JsonViewProps) => {
     const { toast } = useToast();
     const [copied, setCopied] = useState(false);
@@ -86,6 +88,7 @@ const JsonView = memo(
             name={name}
             depth={0}
             initialExpandDepth={initialExpandDepth}
+            isError={isError}
           />
         </div>
       </div>
@@ -100,17 +103,25 @@ interface JsonNodeProps {
   name?: string;
   depth: number;
   initialExpandDepth: number;
+  isError?: boolean;
 }
 
 const JsonNode = memo(
-  ({ data, name, depth = 0, initialExpandDepth }: JsonNodeProps) => {
+  ({
+    data,
+    name,
+    depth = 0,
+    initialExpandDepth,
+    isError = false,
+  }: JsonNodeProps) => {
     const [isExpanded, setIsExpanded] = useState(depth < initialExpandDepth);
     const [typeStyleMap] = useState<Record<string, string>>({
       number: "text-blue-600",
       boolean: "text-amber-600",
       null: "text-purple-600",
       undefined: "text-gray-600",
-      string: "text-green-600 break-all whitespace-pre-wrap",
+      string: "text-green-600 group-hover:text-green-500",
+      error: "text-red-600 group-hover:text-red-500",
       default: "text-gray-700",
     });
     const dataType = getDataType(data);
@@ -214,7 +225,14 @@ const JsonNode = memo(
                 {name}:
               </span>
             )}
-            <pre className={typeStyleMap.string}>"{value}"</pre>
+            <pre
+              className={clsx(
+                typeStyleMap.string,
+                "break-all whitespace-pre-wrap",
+              )}
+            >
+              "{value}"
+            </pre>
           </div>
         );
       }
@@ -228,8 +246,8 @@ const JsonNode = memo(
           )}
           <pre
             className={clsx(
-              typeStyleMap.string,
-              "cursor-pointer group-hover:text-green-500",
+              isError ? typeStyleMap.error : typeStyleMap.string,
+              "cursor-pointer break-all whitespace-pre-wrap",
             )}
             onClick={() => setIsExpanded(!isExpanded)}
             title={isExpanded ? "Click to collapse" : "Click to expand"}
diff --git a/client/src/components/Sidebar.tsx b/client/src/components/Sidebar.tsx
index 31f9b68..a53d337 100644
--- a/client/src/components/Sidebar.tsx
+++ b/client/src/components/Sidebar.tsx
@@ -103,14 +103,19 @@ const Sidebar = ({
       <div className="p-4 flex-1 overflow-auto">
         <div className="space-y-4">
           <div className="space-y-2">
-            <label className="text-sm font-medium">Transport Type</label>
+            <label
+              className="text-sm font-medium"
+              htmlFor="transport-type-select"
+            >
+              Transport Type
+            </label>
             <Select
               value={transportType}
               onValueChange={(value: "stdio" | "sse") =>
                 setTransportType(value)
               }
             >
-              <SelectTrigger>
+              <SelectTrigger id="transport-type-select">
                 <SelectValue placeholder="Select transport type" />
               </SelectTrigger>
               <SelectContent>
@@ -123,8 +128,11 @@ const Sidebar = ({
           {transportType === "stdio" ? (
             <>
               <div className="space-y-2">
-                <label className="text-sm font-medium">Command</label>
+                <label className="text-sm font-medium" htmlFor="command-input">
+                  Command
+                </label>
                 <Input
+                  id="command-input"
                   placeholder="Command"
                   value={command}
                   onChange={(e) => setCommand(e.target.value)}
@@ -132,8 +140,14 @@ const Sidebar = ({
                 />
               </div>
               <div className="space-y-2">
-                <label className="text-sm font-medium">Arguments</label>
+                <label
+                  className="text-sm font-medium"
+                  htmlFor="arguments-input"
+                >
+                  Arguments
+                </label>
                 <Input
+                  id="arguments-input"
                   placeholder="Arguments (space-separated)"
                   value={args}
                   onChange={(e) => setArgs(e.target.value)}
@@ -144,8 +158,11 @@ const Sidebar = ({
           ) : (
             <>
               <div className="space-y-2">
-                <label className="text-sm font-medium">URL</label>
+                <label className="text-sm font-medium" htmlFor="sse-url-input">
+                  URL
+                </label>
                 <Input
+                  id="sse-url-input"
                   placeholder="URL"
                   value={sseUrl}
                   onChange={(e) => setSseUrl(e.target.value)}
@@ -157,6 +174,7 @@ const Sidebar = ({
                   variant="outline"
                   onClick={() => setShowBearerToken(!showBearerToken)}
                   className="flex items-center w-full"
+                  aria-expanded={showBearerToken}
                 >
                   {showBearerToken ? (
                     <ChevronDown className="w-4 h-4 mr-2" />
@@ -167,8 +185,14 @@ const Sidebar = ({
                 </Button>
                 {showBearerToken && (
                   <div className="space-y-2">
-                    <label className="text-sm font-medium">Bearer Token</label>
+                    <label
+                      className="text-sm font-medium"
+                      htmlFor="bearer-token-input"
+                    >
+                      Bearer Token
+                    </label>
                     <Input
+                      id="bearer-token-input"
                       placeholder="Bearer Token"
                       value={bearerToken}
                       onChange={(e) => setBearerToken(e.target.value)}
@@ -187,6 +211,7 @@ const Sidebar = ({
                 onClick={() => setShowEnvVars(!showEnvVars)}
                 className="flex items-center w-full"
                 data-testid="env-vars-button"
+                aria-expanded={showEnvVars}
               >
                 {showEnvVars ? (
                   <ChevronDown className="w-4 h-4 mr-2" />
@@ -201,6 +226,7 @@ const Sidebar = ({
                     <div key={idx} className="space-y-2 pb-4">
                       <div className="flex gap-2">
                         <Input
+                          aria-label={`Environment variable key ${idx + 1}`}
                           placeholder="Key"
                           value={key}
                           onChange={(e) => {
@@ -243,6 +269,7 @@ const Sidebar = ({
                       </div>
                       <div className="flex gap-2">
                         <Input
+                          aria-label={`Environment variable value ${idx + 1}`}
                           type={shownEnvVars.has(key) ? "text" : "password"}
                           placeholder="Value"
                           value={value}
@@ -309,6 +336,7 @@ const Sidebar = ({
               onClick={() => setShowConfig(!showConfig)}
               className="flex items-center w-full"
               data-testid="config-button"
+              aria-expanded={showConfig}
             >
               {showConfig ? (
                 <ChevronDown className="w-4 h-4 mr-2" />
@@ -325,7 +353,10 @@ const Sidebar = ({
                   return (
                     <div key={key} className="space-y-2">
                       <div className="flex items-center gap-1">
-                        <label className="text-sm font-medium text-green-600 break-all">
+                        <label
+                          className="text-sm font-medium text-green-600 break-all"
+                          htmlFor={`${configKey}-input`}
+                        >
                           {configItem.label}
                         </label>
                         <Tooltip>
@@ -339,6 +370,7 @@ const Sidebar = ({
                       </div>
                       {typeof configItem.value === "number" ? (
                         <Input
+                          id={`${configKey}-input`}
                           type="number"
                           data-testid={`${configKey}-input`}
                           value={configItem.value}
@@ -365,7 +397,7 @@ const Sidebar = ({
                             setConfig(newConfig);
                           }}
                         >
-                          <SelectTrigger>
+                          <SelectTrigger id={`${configKey}-input`}>
                             <SelectValue />
                           </SelectTrigger>
                           <SelectContent>
@@ -375,6 +407,7 @@ const Sidebar = ({
                         </Select>
                       ) : (
                         <Input
+                          id={`${configKey}-input`}
                           data-testid={`${configKey}-input`}
                           value={configItem.value}
                           onChange={(e) => {
@@ -454,14 +487,19 @@ const Sidebar = ({
 
             {loggingSupported && connectionStatus === "connected" && (
               <div className="space-y-2">
-                <label className="text-sm font-medium">Logging Level</label>
+                <label
+                  className="text-sm font-medium"
+                  htmlFor="logging-level-select"
+                >
+                  Logging Level
+                </label>
                 <Select
                   value={logLevel}
                   onValueChange={(value: LoggingLevel) =>
                     sendLogLevelRequest(value)
                   }
                 >
-                  <SelectTrigger>
+                  <SelectTrigger id="logging-level-select">
                     <SelectValue placeholder="Select logging level" />
                   </SelectTrigger>
                   <SelectContent>
diff --git a/client/src/components/ToolsTab.tsx b/client/src/components/ToolsTab.tsx
index ea123db..2030ed7 100644
--- a/client/src/components/ToolsTab.tsx
+++ b/client/src/components/ToolsTab.tsx
@@ -69,11 +69,18 @@ const ToolsTab = ({
       return (
         <>
           <h4 className="font-semibold mb-2">
-            Tool Result: {isError ? "Error" : "Success"}
+            Tool Result:{" "}
+            {isError ? (
+              <span className="text-red-600 font-semibold">Error</span>
+            ) : (
+              <span className="text-green-600 font-semibold">Success</span>
+            )}
           </h4>
           {structuredResult.content.map((item, index) => (
             <div key={index} className="mb-2">
-              {item.type === "text" && <JsonView data={item.text} />}
+              {item.type === "text" && (
+                <JsonView data={item.text} isError={isError} />
+              )}
               {item.type === "image" && (
                 <img
                   src={`data:${item.mimeType};base64,${item.data}`}