fix(core): properly handle MCP multi-part tool results in OpenAI converter

packages/core/src/core/coreToolScheduler.test.ts

@@ -889,15 +889,22 @@ describe('convertToFunctionResponse', () => {
       { text: 'Another text part' },
     ];
     const result = convertToFunctionResponse(toolName, callId, llmContent);
+    // All content should be inside the FunctionResponse:
+    // - text parts joined into response.output
+    // - media parts in response.parts
     expect(result).toEqual([
       {
         functionResponse: {
           name: toolName,
           id: callId,
-          response: { output: 'Tool execution succeeded.' },
+          response: {
+            output: 'Some textual description\nAnother text part',
+          },
+          parts: [
+            { inlineData: { mimeType: 'image/jpeg', data: 'base64data...' } },
+          ],
         },
       },
-      ...llmContent,
     ]);
   });
 

packages/core/src/core/coreToolScheduler.ts

@@ -190,12 +190,26 @@ export function convertToFunctionResponse(
   }
 
   if (Array.isArray(contentToProcess)) {
-    const functionResponse = createFunctionResponsePart(
-      callId,
-      toolName,
-      'Tool execution succeeded.',
-    );
-    return [functionResponse, ...toParts(contentToProcess)];
+    // Extract text and media from all parts so that EVERYTHING is inside
+    // the FunctionResponse.
+    const textParts: string[] = [];
+    const mediaParts: FunctionResponsePart[] = [];
+
+    for (const part of toParts(contentToProcess)) {
+      if (part.text !== undefined) {
+        textParts.push(part.text);
+      } else if (part.inlineData) {
+        mediaParts.push({ inlineData: part.inlineData });
+      } else if (part.fileData) {
+        mediaParts.push({ fileData: part.fileData });
+      }
+      // Other exotic part types (e.g. functionCall) are intentionally
+      // dropped here – they should not appear inside tool results.
+    }
+
+    const output =
+      textParts.length > 0 ? textParts.join('\n') : 'Tool execution succeeded.';
+    return [createFunctionResponsePart(callId, toolName, output, mediaParts)];
   }
 
   // After this point, contentToProcess is a single Part object.