fix: ollama fails when tools use optional args (#6343)

## Why are these changes needed?
`convert_tools` failed if Optional args were used in tools (the `type`
field doesn't exist in that case and `anyOf` must be used).

This uses the `anyOf` field to pick the first non-null type to use.  

## Related issue number

Fixes #6323

## Checks

- [ ] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [x] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [x] I've made sure all auto checks have passed.

---------

Signed-off-by: Peter Jausovec <peter.jausovec@solo.io>
Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

python/packages/autogen-ext/src/autogen_ext/models/ollama/_ollama_client.py

@@ -315,8 +315,17 @@ def convert_tools(
         if parameters is not None:
             ollama_properties = {}
             for prop_name, prop_schema in parameters["properties"].items():
+                # Determine property type, checking "type" first, then "anyOf", defaulting to "string"
+                prop_type = prop_schema.get("type")
+                if prop_type is None and "anyOf" in prop_schema:
+                    prop_type = next(
+                        (opt.get("type") for opt in prop_schema["anyOf"] if opt.get("type") != "null"),
+                        None,  # Default to None if no non-null type found in anyOf
+                    )
+                prop_type = prop_type or "string"
+
                 ollama_properties[prop_name] = OllamaTool.Function.Parameters.Property(
-                    type=prop_schema["type"],
+                    type=prop_type,
                     description=prop_schema["description"] if "description" in prop_schema else None,
                 )
         result.append(

python/packages/autogen-ext/tests/models/test_ollama_chat_completion_client.py

@@ -1,6 +1,6 @@
 import json
 import logging
-from typing import Any, AsyncGenerator, Dict, List, Mapping
+from typing import Any, AsyncGenerator, Dict, List, Mapping, Optional
 
 import httpx
 import pytest
@@ -13,11 +13,11 @@ from autogen_core.models import (
     FunctionExecutionResultMessage,
     UserMessage,
 )
-from autogen_core.tools import FunctionTool
+from autogen_core.tools import FunctionTool, ToolSchema
 from autogen_ext.models.ollama import OllamaChatCompletionClient
-from autogen_ext.models.ollama._ollama_client import OLLAMA_VALID_CREATE_KWARGS_KEYS
+from autogen_ext.models.ollama._ollama_client import OLLAMA_VALID_CREATE_KWARGS_KEYS, convert_tools
 from httpx import Response
-from ollama import AsyncClient, ChatResponse, Message
+from ollama import AsyncClient, ChatResponse, Message, Tool
 from pydantic import BaseModel
 
 
@@ -206,6 +206,46 @@ async def test_create_tools(monkeypatch: pytest.MonkeyPatch) -> None:
     assert create_result.usage.completion_tokens == 12
 
 
+@pytest.mark.asyncio
+async def test_convert_tools() -> None:
+    def add(x: int, y: Optional[int]) -> str:
+        if y is None:
+            return str(x)
+        return str(x + y)
+
+    add_tool = FunctionTool(add, description="Add two numbers")
+
+    tool_schema_noparam: ToolSchema = {
+        "name": "manual_tool",
+        "description": "A tool defined manually",
+        "parameters": {
+            "type": "object",
+            "properties": {
+                "param_with_type": {"type": "integer", "description": "An integer param"},
+                "param_without_type": {"description": "A param without explicit type"},
+            },
+            "required": ["param_with_type"],
+        },
+    }
+
+    converted_tools = convert_tools([add_tool, tool_schema_noparam])
+    assert len(converted_tools) == 2
+    assert isinstance(converted_tools[0].function, Tool.Function)
+    assert isinstance(converted_tools[0].function.parameters, Tool.Function.Parameters)
+    assert converted_tools[0].function.parameters.properties is not None
+    assert converted_tools[0].function.name == add_tool.name
+    assert converted_tools[0].function.parameters.properties["y"].type == "integer"
+
+    # test it defaults to string
+    assert isinstance(converted_tools[1].function, Tool.Function)
+    assert isinstance(converted_tools[1].function.parameters, Tool.Function.Parameters)
+    assert converted_tools[1].function.parameters.properties is not None
+    assert converted_tools[1].function.name == "manual_tool"
+    assert converted_tools[1].function.parameters.properties["param_with_type"].type == "integer"
+    assert converted_tools[1].function.parameters.properties["param_without_type"].type == "string"
+    assert converted_tools[1].function.parameters.required == ["param_with_type"]
+
+
 @pytest.mark.asyncio
 async def test_create_stream_tools(monkeypatch: pytest.MonkeyPatch) -> None:
     def add(x: int, y: int) -> str: