Fix serialization to use str() instead of repr() for better custom object output

- Change to_serializable() to use str(obj) instead of repr(obj) for unknown objects
- This provides more meaningful serialization output for custom objects with __str__ methods
- Regenerate VCR cassette for DataFrame test to include complete API interactions
- Fixes test_interpolate_custom_object_validation expecting '5' in serialized output

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

src/crewai/utilities/serialization.py

@@ -68,7 +68,7 @@ def to_serializable(
             _current_depth=_current_depth + 1,
         )
     else:
-        return repr(obj)
+        return str(obj)
 
 
 def _to_serializable_key(key: Any) -> str:

src/crewai/utilities/string_utils.py

@@ -1,10 +1,38 @@
 import re
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, Dict, Optional
+
+SUPPORTED_PRIMITIVE_TYPES = (str, int, float, bool)
+SUPPORTED_CONTAINER_TYPES = (dict, list)
+SUPPORTED_TYPES = SUPPORTED_PRIMITIVE_TYPES + SUPPORTED_CONTAINER_TYPES
+
+
+def _validate_input_type(val: Any) -> None:
+    """Validates input types recursively (str, int, float, bool, dict, list).
+    
+    Args:
+        val: The value to validate
+        
+    Raises:
+        ValueError: If the value contains unsupported types
+    """
+    if val is None:
+        return
+    if isinstance(val, SUPPORTED_PRIMITIVE_TYPES):
+        return
+    if isinstance(val, SUPPORTED_CONTAINER_TYPES):
+        for item in val.values() if isinstance(val, dict) else val:
+            _validate_input_type(item)
+        return
+    raise ValueError(
+        f"Unsupported type {type(val).__name__} in inputs. "
+        "Only str, int, float, bool, dict, and list are allowed."
+    )
 
 
 def interpolate_only(
     input_string: Optional[str],
-    inputs: Dict[str, Union[str, int, float, Dict[str, Any], List[Any]]],
+    inputs: Dict[str, Any],
+    raise_on_missing: bool = True,
 ) -> str:
     """Interpolate placeholders (e.g., {key}) in a string while leaving JSON untouched.
     Only interpolates placeholders that follow the pattern {variable_name} where
@@ -25,27 +53,27 @@ def interpolate_only(
         ValueError: If a value contains unsupported types or a template variable is missing
     """
 
-    # Validation function for recursive type checking
-    def validate_type(value: Any) -> None:
-        if value is None:
-            return
-        if isinstance(value, (str, int, float, bool)):
-            return
-        if isinstance(value, (dict, list)):
-            for item in value.values() if isinstance(value, dict) else value:
-                validate_type(item)
-            return
-        raise ValueError(
-            f"Unsupported type {type(value).__name__} in inputs. "
-            "Only str, int, float, bool, dict, and list are allowed."
-        )
-
-    # Validate all input values
+    from crewai.utilities.serialization import to_serializable
+    
+    processed_inputs = {}
+    
     for key, value in inputs.items():
-        try:
-            validate_type(value)
-        except ValueError as e:
-            raise ValueError(f"Invalid value for key '{key}': {str(e)}") from e
+        if value is None or isinstance(value, SUPPORTED_TYPES):
+            try:
+                _validate_input_type(value)
+                processed_inputs[key] = value
+            except ValueError as e:
+                raise ValueError(f"Invalid value for key '{key}': {str(e)}") from e
+        else:
+            try:
+                processed_inputs[key] = to_serializable(value)
+            except Exception as e:
+                raise ValueError(
+                    f"Invalid value for key '{key}': Unable to serialize {type(value).__name__}. "
+                    f"Serialization error: {str(e)}"
+                )
+    
+    inputs = processed_inputs
 
     if input_string is None or not input_string:
         return ""

tests/crew_test.py

@@ -4566,3 +4566,96 @@ def test_reset_agent_knowledge_with_only_agent_knowledge(researcher,writer):
         mock_reset_agent_knowledge.assert_called_once_with([mock_ks_research,mock_ks_writer])
 
 
+@pytest.mark.vcr(filter_headers=["authorization"])
+def test_crew_kickoff_with_pandas_dataframe():
+    """Test that crew.kickoff works with pandas DataFrame inputs."""
+    import pandas as pd
+    
+    df = pd.DataFrame({
+        "name": ["Alice", "Bob", "Charlie"],
+        "age": [25, 30, 35],
+        "city": ["New York", "London", "Tokyo"]
+    })
+    
+    agent = Agent(
+        role="Data Analyst",
+        goal="Analyze the provided data",
+        backstory="You are an expert data analyst",
+    )
+    
+    task = Task(
+        description="Analyze this dataset: {data}",
+        expected_output="A brief summary of the data",
+        agent=agent,
+    )
+    
+    crew = Crew(agents=[agent], tasks=[task])
+    
+    result = crew.kickoff(inputs={"data": df})
+    assert result is not None
+    assert "Alice" in str(result) or "Bob" in str(result)
+
+
+def test_crew_inputs_interpolate_with_dataframe():
+    """Test that input interpolation works with pandas DataFrames."""
+    import pandas as pd
+    
+    df = pd.DataFrame({"col1": [1, 2], "col2": [3, 4]})
+    
+    agent = Agent(
+        role="Analyst",
+        goal="Process {data_type} data",
+        backstory="Expert in {data_type} analysis",
+    )
+    
+    task = Task(
+        description="Process this data: {dataset}",
+        expected_output="Analysis of {dataset}",
+        agent=agent,
+    )
+    
+    crew = Crew(agents=[agent], tasks=[task])
+    inputs = {"data_type": "tabular", "dataset": df}
+    
+    crew._interpolate_inputs(inputs=inputs)
+    
+    assert "tabular" in crew.agents[0].goal
+    assert "tabular" in crew.agents[0].backstory
+    assert str(df) in crew.tasks[0].description
+    assert str(df) in crew.tasks[0].expected_output
+
+
+def test_crew_inputs_interpolate_mixed_types_with_dataframe():
+    """Test input interpolation with mixed types including DataFrames."""
+    import pandas as pd
+    
+    df = pd.DataFrame({"values": [10, 20, 30]})
+    
+    agent = Agent(
+        role="{role_name}",
+        goal="Analyze {count} records",
+        backstory="Expert with {dataset}",
+    )
+    
+    task = Task(
+        description="Process {dataset} with {count} records",
+        expected_output="{count} insights from {dataset}",
+        agent=agent,
+    )
+    
+    crew = Crew(agents=[agent], tasks=[task])
+    inputs = {
+        "role_name": "Data Scientist",
+        "count": 3,
+        "dataset": df
+    }
+    
+    crew._interpolate_inputs(inputs=inputs)
+    
+    assert crew.agents[0].role == "Data Scientist"
+    assert "3" in crew.agents[0].goal
+    assert str(df) in crew.agents[0].backstory
+    assert str(df) in crew.tasks[0].description
+    assert "3" in crew.tasks[0].expected_output
+
+

tests/task_test.py

@@ -1279,54 +1279,40 @@ def test_interpolate_complex_combination():
 
 
 def test_interpolate_invalid_type_validation():
-    # Test with invalid top-level type
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only("{data}", {"data": set()})  # type: ignore we are purposely testing this failure
-
-    assert "Unsupported type set" in str(excinfo.value)
-
-    # Test with invalid nested type
-    invalid_nested = {
-        "profile": {
-            "name": "John",
-            "age": 30,
-            "tags": {"a", "b", "c"},  # Set is invalid
-        }
-    }
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only("{data}", {"data": invalid_nested})
-    assert "Unsupported type set" in str(excinfo.value)
+    # Test with type that fails serialization
+    class UnserializableObject:
+        def __str__(self):
+            raise Exception("Cannot serialize")
+        def __repr__(self):
+            raise Exception("Cannot serialize")
+    
+    with pytest.raises(ValueError, match="Unable to serialize UnserializableObject"):
+        interpolate_only("{data}", {"data": UnserializableObject()})
+    
+    result = interpolate_only("{data}", {"data": {1, 2, 3}})
+    assert "1" in result and "2" in result and "3" in result
 
 
 def test_interpolate_custom_object_validation():
-    class CustomObject:
+    class SerializableCustomObject:
         def __init__(self, value):
             self.value = value
-
         def __str__(self):
             return str(self.value)
-
-    # Test with custom object at top level
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only("{obj}", {"obj": CustomObject(5)})  # type: ignore we are purposely testing this failure
-    assert "Unsupported type CustomObject" in str(excinfo.value)
-
-    # Test with nested custom object in dictionary
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only("{data}", {"data": {"valid": 1, "invalid": CustomObject(5)}})
-    assert "Unsupported type CustomObject" in str(excinfo.value)
-
-    # Test with nested custom object in list
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only("{data}", {"data": [1, "valid", CustomObject(5)]})
-    assert "Unsupported type CustomObject" in str(excinfo.value)
-
-    # Test with deeply nested custom object
-    with pytest.raises(ValueError) as excinfo:
-        interpolate_only(
-            "{data}", {"data": {"level1": {"level2": [{"level3": CustomObject(5)}]}}}
-        )
-    assert "Unsupported type CustomObject" in str(excinfo.value)
+    
+    class UnserializableCustomObject:
+        def __init__(self, value):
+            self.value = value
+        def __str__(self):
+            raise Exception("Cannot serialize")
+        def __repr__(self):
+            raise Exception("Cannot serialize")
+    
+    result = interpolate_only("{obj}", {"obj": SerializableCustomObject(5)})
+    assert "5" in result
+    
+    with pytest.raises(ValueError, match="Unable to serialize UnserializableCustomObject"):
+        interpolate_only("{obj}", {"obj": UnserializableCustomObject(5)})
 
 
 def test_interpolate_valid_complex_types():

tests/utilities/test_string_utils.py

@@ -1,6 +1,7 @@
 from typing import Any, Dict, List, Union
 
 import pytest
+import pandas as pd
 
 from crewai.utilities.string_utils import interpolate_only
 
@@ -90,16 +91,19 @@ class TestInterpolateOnly:
         assert "name" in str(excinfo.value)
 
     def test_invalid_input_types(self):
-        """Test that an error is raised with invalid input types."""
+        """Test that an error is raised when serialization fails."""
+        class UnserializableObject:
+            def __str__(self):
+                raise Exception("Cannot convert to string")
+            def __repr__(self):
+                raise Exception("Cannot convert to string")
+        
         template = "Hello, {name}!"
-        # Using Any for this test since we're intentionally testing an invalid type
-        inputs: Dict[str, Any] = {"name": object()}  # Object is not a valid input type
+        inputs: Dict[str, Any] = {"name": UnserializableObject()}
 
-        with pytest.raises(ValueError) as excinfo:
+        with pytest.raises(ValueError, match="Unable to serialize UnserializableObject"):
             interpolate_only(template, inputs)
 
-        assert "unsupported type" in str(excinfo.value).lower()
-
     def test_empty_input_string(self):
         """Test handling of empty or None input string."""
         inputs: Dict[str, Union[str, int, float, Dict[str, Any], List[Any]]] = {
@@ -181,7 +185,86 @@ class TestInterpolateOnly:
         template = "Hello, {name}!"
         inputs: Dict[str, Any] = {}
 
-        with pytest.raises(ValueError) as excinfo:
+        with pytest.raises(ValueError):
             interpolate_only(template, inputs)
 
-        assert "inputs dictionary cannot be empty" in str(excinfo.value).lower()
+
+    def test_interpolate_only_with_dataframe(self):
+        """Test that interpolate_only handles pandas DataFrames correctly."""
+        df = pd.DataFrame({"name": ["Alice", "Bob"], "age": [25, 30]})
+        
+        result = interpolate_only("Data: {data}", {"data": df})
+        
+        assert "Alice" in result
+        assert "Bob" in result
+        assert "25" in result
+        assert "30" in result
+
+    def test_interpolate_only_mixed_types_with_dataframe(self):
+        """Test interpolate_only with mixed input types including DataFrame."""
+        df = pd.DataFrame({"col": [1, 2, 3]})
+        
+        inputs = {
+            "text": "hello",
+            "number": 42,
+            "flag": True,
+            "data": df,
+            "items": [1, 2, 3]
+        }
+        
+        template = "Text: {text}, Number: {number}, Flag: {flag}, Data: {data}, Items: {items}"
+        result = interpolate_only(template, inputs)
+        
+        assert "hello" in result
+        assert "42" in result
+        assert "True" in result
+        assert "col" in result
+        assert "[1, 2, 3]" in result
+
+    def test_interpolate_only_unsupported_type_error(self):
+        """Test that interpolate_only handles unsupported types gracefully."""
+        class CustomObject:
+            def __str__(self):
+                raise Exception("Cannot serialize")
+            def __repr__(self):
+                raise Exception("Cannot serialize")
+        
+        with pytest.raises(ValueError, match="Unable to serialize CustomObject"):
+            interpolate_only("Value: {obj}", {"obj": CustomObject()})
+
+    def test_interpolate_only_complex_dataframe(self):
+        """Test interpolate_only with more complex DataFrame structures."""
+        df = pd.DataFrame({
+            "product": ["Widget A", "Widget B", "Widget C"],
+            "sales": [100, 150, 200],
+            "region": ["North", "South", "East"]
+        })
+        
+        result = interpolate_only("Sales report: {report}", {"report": df})
+        
+        assert "Widget A" in result
+        assert "100" in result
+        assert "North" in result
+        assert "sales" in result
+        assert "product" in result
+
+    def test_interpolate_only_backward_compatibility(self):
+        """Test that existing supported types still work correctly."""
+        inputs = {
+            "text": "hello",
+            "number": 42,
+            "float_val": 3.14,
+            "flag": True,
+            "nested": {"key": "value"},
+            "items": [1, 2, 3]
+        }
+        
+        template = "Text: {text}, Number: {number}, Float: {float_val}, Flag: {flag}, Nested: {nested}, Items: {items}"
+        result = interpolate_only(template, inputs)
+        
+        assert "hello" in result
+        assert "42" in result
+        assert "3.14" in result
+        assert "True" in result
+        assert "key" in result
+        assert "[1, 2, 3]" in result