fix(core): support Pydantic metadata descriptions

python/packages/autogen-core/src/autogen_core/_function_utils.py

@@ -117,16 +117,15 @@ class ToolFunction(BaseModel):
     function: Annotated[Function, Field(description="Function under tool")]
 
 
-def type2description(k: str, v: Union[Annotated[Type[Any], str], Type[Any]]) -> str:
-    # handles Annotated
+def type2description(k: str, v: Any) -> str:
     if hasattr(v, "__metadata__"):
-        retval = v.__metadata__[0]
-        if isinstance(retval, str):
-            return retval
-        else:
-            raise ValueError(f"Invalid description {retval} for parameter {k}, should be a string.")
-    else:
-        return k
+        for metadata in v.__metadata__:
+            if isinstance(metadata, str):
+                return metadata
+            description = getattr(metadata, "description", None)
+            if isinstance(description, str):
+                return description
+    return k
 
 
 def get_parameter_json_schema(k: str, v: Any, default_values: Dict[str, Any]) -> Dict[str, Any]:

python/packages/autogen-core/tests/test_tools.py

@@ -5,7 +5,7 @@
 
 import pytest
 from autogen_core import CancellationToken
-from autogen_core._function_utils import get_typed_signature
+from autogen_core._function_utils import get_typed_signature, type2description
 from autogen_core.tools import BaseTool, FunctionTool
 from autogen_core.tools._base import ToolSchema
 from pydantic import BaseModel, Field, ValidationError, model_serializer
@@ -94,6 +94,32 @@ def my_function(arg: str, other: Annotated[int, "int arg"], nonrequired: int = 5
     assert len(schema["parameters"]["properties"]) == 3
 
 
+def test_func_tool_schema_generation_with_annotated_metadata() -> None:
+    def my_function(
+        query: Annotated[str, Field(description="SQL search term")],
+        score: Annotated[float, Field(gt=0), "Normalized score"],
+        limit: Annotated[int, Field(ge=0)],
+    ) -> str:
+        return "result"
+
+    schema = FunctionTool(my_function, description="Function tool.").schema
+    assert "parameters" in schema
+    properties = schema["parameters"]["properties"]
+
+    assert properties["query"]["description"] == "SQL search term"
+    assert properties["score"]["description"] == "Normalized score"
+    assert properties["limit"]["description"] == "limit"
+
+
+def test_type2description_uses_description_attribute() -> None:
+    class DescribedMetadata:
+        description = "Custom description"
+
+    annotation = Annotated[int, object(), DescribedMetadata()]
+
+    assert type2description("value", annotation) == "Custom description"
+
+
 def test_func_tool_schema_generation_strict() -> None:
     def my_function1(arg: str, other: Annotated[int, "int arg"], nonrequired: int = 5) -> MyResult:
         return MyResult(result="test")