Fix Ollama models ValueError when response_format is used

- Add _is_ollama_model method to detect Ollama models consistently
- Skip response_format validation for Ollama models in _validate_call_params
- Filter out response_format parameter for Ollama models in _prepare_completion_params
- Add comprehensive tests for Ollama response_format handling
- Maintain backward compatibility for other LLM providers

Fixes #3082

Co-Authored-By: João <joao@crewai.com>

test_ollama_fix.py

@@ -0,0 +1,77 @@
+"""
+Reproduction script for issue #3082 - Ollama response_format error.
+This script reproduces the original issue and verifies the fix.
+"""
+
+from pydantic import BaseModel
+from crewai.llm import LLM
+from crewai import Agent
+
+class GuideOutline(BaseModel):
+    title: str
+    sections: list[str]
+
+def test_original_issue():
+    """Test the original issue scenario from the GitHub issue."""
+    print("Testing original issue scenario...")
+    
+    try:
+        llm = LLM(model="ollama/gemma3:latest", response_format=GuideOutline)
+        print("✅ LLM creation with response_format succeeded")
+        
+        params = llm._prepare_completion_params("Test message")
+        if "response_format" not in params or params.get("response_format") is None:
+            print("✅ response_format correctly filtered out for Ollama model")
+        else:
+            print("❌ response_format was not filtered out")
+            
+        agent = Agent(
+            role="Guide Creator",
+            goal="Create comprehensive guides",
+            backstory="You are an expert at creating structured guides",
+            llm=llm
+        )
+        print("✅ Agent creation with Ollama LLM succeeded")
+        
+    except ValueError as e:
+        if "does not support response_format" in str(e):
+            print(f"❌ Original issue still exists: {e}")
+            return False
+        else:
+            print(f"❌ Unexpected ValueError: {e}")
+            return False
+    except Exception as e:
+        print(f"❌ Unexpected error: {e}")
+        return False
+    
+    return True
+
+def test_non_ollama_models():
+    """Test that non-Ollama models still work with response_format."""
+    print("\nTesting non-Ollama models...")
+    
+    try:
+        llm = LLM(model="gpt-4", response_format=GuideOutline)
+        params = llm._prepare_completion_params("Test message")
+        
+        if params.get("response_format") == GuideOutline:
+            print("✅ Non-Ollama models still include response_format")
+            return True
+        else:
+            print("❌ Non-Ollama models missing response_format")
+            return False
+            
+    except Exception as e:
+        print(f"❌ Error with non-Ollama model: {e}")
+        return False
+
+if __name__ == "__main__":
+    print("Testing Ollama response_format fix...")
+    
+    success1 = test_original_issue()
+    success2 = test_non_ollama_models()
+    
+    if success1 and success2:
+        print("\n🎉 All tests passed! The fix is working correctly.")
+    else:
+        print("\n💥 Some tests failed. The fix needs more work.")