diff --git a/src/services/enhanced-config-validator.ts b/src/services/enhanced-config-validator.ts
index 472d224..6c652ce 100644
--- a/src/services/enhanced-config-validator.ts
+++ b/src/services/enhanced-config-validator.ts
@@ -415,9 +415,19 @@ export class EnhancedConfigValidator extends ConfigValidator {
     }
 
     // 2. Suggest responseFormat for API endpoints
-    const isApiEndpoint = url.includes('/api') || url.includes('/rest') ||
-                          url.includes('supabase') || url.includes('firebase') ||
-                          url.includes('googleapis') || url.includes('.com/v');
+    const lowerUrl = url.toLowerCase();
+    const isApiEndpoint =
+      // Subdomain patterns (api.example.com)
+      /^https?:\/\/api\./i.test(url) ||
+      // Path patterns with word boundaries to prevent false positives like "therapist", "restaurant"
+      /\/api[\/\?]|\/api$/i.test(url) ||
+      /\/rest[\/\?]|\/rest$/i.test(url) ||
+      // Known API service domains
+      lowerUrl.includes('supabase.co') ||
+      lowerUrl.includes('firebase') ||
+      lowerUrl.includes('googleapis.com') ||
+      // Versioned API paths (e.g., example.com/v1, example.com/v2)
+      /\.com\/v\d+/i.test(url);
 
     if (isApiEndpoint && !options.response?.response?.responseFormat) {
       result.suggestions.push(
@@ -431,10 +441,11 @@ export class EnhancedConfigValidator extends ConfigValidator {
     if (url && url.startsWith('=')) {
       // Expression-based URL - check for common protocol issues
       const expressionContent = url.slice(1); // Remove = prefix
+      const lowerExpression = expressionContent.toLowerCase();
 
-      // Check for missing protocol in expression
+      // Check for missing protocol in expression (case-insensitive)
       if (expressionContent.startsWith('www.') ||
-          (expressionContent.includes('{{') && !expressionContent.includes('http'))) {
+          (expressionContent.includes('{{') && !lowerExpression.includes('http'))) {
         result.warnings.push({
           type: 'invalid_value',
           property: 'url',
diff --git a/tests/unit/services/enhanced-config-validator.test.ts b/tests/unit/services/enhanced-config-validator.test.ts
index e3217f6..64df123 100644
--- a/tests/unit/services/enhanced-config-validator.test.ts
+++ b/tests/unit/services/enhanced-config-validator.test.ts
@@ -1020,5 +1020,117 @@ describe('EnhancedConfigValidator', () => {
       );
       expect(responseFormatSuggestion).toBeUndefined();
     });
+
+    it('should detect missing protocol in expressions with uppercase HTTP', () => {
+      const nodeType = 'nodes-base.httpRequest';
+      const config = {
+        url: '={{ "HTTP://" + $json.domain + ".com" }}',
+        method: 'GET'
+      };
+      const properties = [
+        { name: 'url', type: 'string', required: true }
+      ];
+
+      const result = EnhancedConfigValidator.validateWithMode(
+        nodeType,
+        config,
+        properties,
+        'operation',
+        'ai-friendly'
+      );
+
+      // Should NOT warn because HTTP:// is present (case-insensitive)
+      expect(result.warnings).toHaveLength(0);
+    });
+
+    it('should NOT suggest responseFormat for false positive URLs', () => {
+      const nodeType = 'nodes-base.httpRequest';
+      const testUrls = [
+        'https://example.com/therapist-directory',
+        'https://restaurant-bookings.com/reserve',
+        'https://forest-management.org/data'
+      ];
+
+      testUrls.forEach(url => {
+        const config = {
+          url,
+          method: 'GET',
+          options: {}
+        };
+        const properties = [
+          { name: 'url', type: 'string', required: true }
+        ];
+
+        const result = EnhancedConfigValidator.validateWithMode(
+          nodeType,
+          config,
+          properties,
+          'operation',
+          'ai-friendly'
+        );
+
+        const responseFormatSuggestion = result.suggestions.find(
+          (s: string) => s.includes('responseFormat')
+        );
+        expect(responseFormatSuggestion).toBeUndefined();
+      });
+    });
+
+    it('should suggest responseFormat for case-insensitive API paths', () => {
+      const nodeType = 'nodes-base.httpRequest';
+      const testUrls = [
+        'https://example.com/API/users',
+        'https://example.com/Rest/data',
+        'https://example.com/REST/v1/items'
+      ];
+
+      testUrls.forEach(url => {
+        const config = {
+          url,
+          method: 'GET',
+          options: {}
+        };
+        const properties = [
+          { name: 'url', type: 'string', required: true }
+        ];
+
+        const result = EnhancedConfigValidator.validateWithMode(
+          nodeType,
+          config,
+          properties,
+          'operation',
+          'ai-friendly'
+        );
+
+        expect(result.suggestions).toContainEqual(
+          expect.stringContaining('responseFormat')
+        );
+      });
+    });
+
+    it('should handle null and undefined URLs gracefully', () => {
+      const nodeType = 'nodes-base.httpRequest';
+      const testConfigs = [
+        { url: null, method: 'GET' },
+        { url: undefined, method: 'GET' },
+        { url: '', method: 'GET' }
+      ];
+
+      testConfigs.forEach(config => {
+        const properties = [
+          { name: 'url', type: 'string', required: true }
+        ];
+
+        expect(() => {
+          EnhancedConfigValidator.validateWithMode(
+            nodeType,
+            config,
+            properties,
+            'operation',
+            'ai-friendly'
+          );
+        }).not.toThrow();
+      });
+    });
   });
 });
\ No newline at end of file