diff --git a/packages/api/src/mcp/__tests__/parsers.test.ts b/packages/api/src/mcp/__tests__/parsers.test.ts
index afc3fd9de3..0e9bc8ff0a 100644
--- a/packages/api/src/mcp/__tests__/parsers.test.ts
+++ b/packages/api/src/mcp/__tests__/parsers.test.ts
@@ -29,6 +29,72 @@ describe('formatToolContent', () => {
       expect(content).toBe('(No response)');
       expect(artifacts).toBeUndefined();
     });
+
+    it('should return string for known non-OpenAI providers', () => {
+      const result: t.MCPToolCallResponse = {
+        content: [{ type: 'text', text: 'Test content' }],
+      };
+      const [content] = formatToolContent(result, 'google' as t.Provider);
+      // Google is recognized but uses array format, so this should be an array
+      expect(Array.isArray(content)).toBe(true);
+    });
+  });
+
+  describe('automatic detection of OpenAI-compatible custom endpoints', () => {
+    it('should automatically recognize new OpenAI-compatible custom endpoints', () => {
+      const result: t.MCPToolCallResponse = {
+        content: [
+          { type: 'text', text: 'First text' },
+          { type: 'text', text: 'Second text' },
+        ],
+      };
+
+      // Test with a custom endpoint that's not explicitly listed
+      const [content, artifacts] = formatToolContent(result, 'scaleway' as t.Provider);
+      // Should be recognized and use array format (OpenAI-compatible)
+      expect(Array.isArray(content)).toBe(true);
+      expect(content).toEqual([{ type: 'text', text: 'First text\n\nSecond text' }]);
+      expect(artifacts).toBeUndefined();
+    });
+
+    it('should use array format for unknown OpenAI-compatible endpoints', () => {
+      const result: t.MCPToolCallResponse = {
+        content: [
+          { type: 'text', text: 'Before image' },
+          { type: 'image', data: 'base64data', mimeType: 'image/png' },
+          { type: 'text', text: 'After image' },
+        ],
+      };
+
+      // Test with another custom endpoint (e.g., together, perplexity, anyscale)
+      const [content, artifacts] = formatToolContent(result, 'together' as t.Provider);
+      // Should use array format like OpenAI
+      expect(Array.isArray(content)).toBe(true);
+      expect(content).toEqual([
+        { type: 'text', text: 'Before image' },
+        { type: 'text', text: 'After image' },
+      ]);
+      expect(artifacts).toEqual({
+        content: [
+          {
+            type: 'image_url',
+            image_url: { url: 'data:image/png;base64,base64data' },
+          },
+        ],
+      });
+    });
+
+    it('should NOT recognize known non-OpenAI providers', () => {
+      const result: t.MCPToolCallResponse = {
+        content: [{ type: 'text', text: 'Test content' }],
+      };
+
+      // Non-OpenAI providers should return string format
+      const [content, artifacts] = formatToolContent(result, 'bedrock' as t.Provider);
+      expect(typeof content).toBe('string');
+      expect(content).toBe('Test content');
+      expect(artifacts).toBeUndefined();
+    });
   });
 
   describe('recognized providers', () => {
diff --git a/packages/api/src/mcp/parsers.ts b/packages/api/src/mcp/parsers.ts
index c9b824e782..4b81d5b5b0 100644
--- a/packages/api/src/mcp/parsers.ts
+++ b/packages/api/src/mcp/parsers.ts
@@ -7,6 +7,10 @@ function generateResourceId(text: string): string {
   return crypto.createHash('sha256').update(text).digest('hex').substring(0, 10);
 }
 
+// Known providers that are NOT OpenAI-compatible
+// This is a small, stable list that rarely changes
+const NON_OPENAI_PROVIDERS = new Set(['google', 'anthropic', 'bedrock', 'ollama']);
+
 const RECOGNIZED_PROVIDERS = new Set([
   'google',
   'anthropic',
@@ -17,8 +21,32 @@ const RECOGNIZED_PROVIDERS = new Set([
   'deepseek',
   'ollama',
   'bedrock',
+  // Note: Custom OpenAI-compatible endpoints (like scaleway, together, perplexity, etc.)
+  // are automatically recognized if they're not in NON_OPENAI_PROVIDERS
 ]);
 
+/**
+ * Check if a provider should receive structured content formatting for MCP tool responses.
+ *
+ * Recognizes:
+ * 1. Explicitly listed providers in RECOGNIZED_PROVIDERS
+ * 2. Custom OpenAI-compatible endpoints (any provider not in NON_OPENAI_PROVIDERS)
+ *
+ * Custom endpoints are passed with their endpoint name (not "openai"), so we automatically
+ * detect them rather than requiring explicit additions for each new provider.
+ */
+function isRecognizedProvider(provider: t.Provider): boolean {
+  if (RECOGNIZED_PROVIDERS.has(provider)) {
+    return true;
+  }
+
+  if (!NON_OPENAI_PROVIDERS.has(provider)) {
+    return true;
+  }
+
+  return false;
+}
+
 const imageFormatters: Record<string, undefined | t.ImageFormatter> = {
   // google: (item) => ({
   //   type: 'image',
@@ -92,7 +120,7 @@ export function formatToolContent(
   result: t.MCPToolCallResponse,
   provider: t.Provider,
 ): t.FormattedContentResult {
-  if (!RECOGNIZED_PROVIDERS.has(provider)) {
+  if (!isRecognizedProvider(provider)) {
     return [parseAsString(result), undefined];
   }