fix: mcp tool with array type should include items

# What does this PR do?


## Test Plan

llama_stack/providers/inline/agents/meta_reference/responses/streaming.py

@@ -568,6 +568,7 @@ class StreamingResponseOrchestrator:
                                 description=param.description,
                                 required=param.required,
                                 default=param.default,
+                                items=param.items,
                             )
                             for param in t.parameters
                         },

tests/unit/providers/agents/meta_reference/responses/__init__.py

@@ -0,0 +1,5 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.

tests/unit/providers/agents/meta_reference/responses/test_streaming.py

@@ -0,0 +1,147 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+"""
+Unit tests for MCP tool parameter conversion in streaming responses.
+
+This tests the fix for handling array-type parameters with 'items' field
+when converting MCP tool definitions to OpenAI format.
+"""
+
+from llama_stack.apis.tools import ToolParameter
+from llama_stack.models.llama.datatypes import ToolDefinition, ToolParamDefinition
+from llama_stack.providers.utils.inference.openai_compat import convert_tooldef_to_openai_tool
+
+
+def test_mcp_tool_conversion_with_array_items():
+    """
+    Test that MCP tool parameters with array type and items field are properly converted.
+
+    This is a regression test for the bug where array parameters without 'items'
+    caused OpenAI API validation errors like:
+    "Invalid schema for function 'pods_exec': In context=('properties', 'command'),
+    array schema missing items."
+    """
+    # Create a tool parameter with array type and items specification
+    # This mimics what kubernetes-mcp-server's pods_exec tool has
+    tool_param = ToolParameter(
+        name="command",
+        parameter_type="array",
+        description="Command to execute in the pod",
+        required=True,
+        items={"type": "string"},  # This is the crucial field
+    )
+
+    # Convert to ToolDefinition format (as done in streaming.py)
+    tool_def = ToolDefinition(
+        tool_name="test_tool",
+        description="Test tool with array parameter",
+        parameters={
+            "command": ToolParamDefinition(
+                param_type=tool_param.parameter_type,
+                description=tool_param.description,
+                required=tool_param.required,
+                default=tool_param.default,
+                items=tool_param.items,  # The fix: ensure items is passed through
+            )
+        },
+    )
+
+    # Convert to OpenAI format
+    openai_tool = convert_tooldef_to_openai_tool(tool_def)
+
+    # Verify the conversion includes the items field
+    assert openai_tool["type"] == "function"
+    assert openai_tool["function"]["name"] == "test_tool"
+    assert "parameters" in openai_tool["function"]
+
+    parameters = openai_tool["function"]["parameters"]
+    assert "properties" in parameters
+    assert "command" in parameters["properties"]
+
+    command_param = parameters["properties"]["command"]
+    assert command_param["type"] == "array"
+    assert "items" in command_param, "Array parameter must have 'items' field for OpenAI API"
+    assert command_param["items"] == {"type": "string"}
+
+
+def test_mcp_tool_conversion_without_array():
+    """Test that non-array parameters work correctly without items field."""
+    tool_param = ToolParameter(
+        name="name",
+        parameter_type="string",
+        description="Name parameter",
+        required=True,
+    )
+
+    tool_def = ToolDefinition(
+        tool_name="test_tool",
+        description="Test tool with string parameter",
+        parameters={
+            "name": ToolParamDefinition(
+                param_type=tool_param.parameter_type,
+                description=tool_param.description,
+                required=tool_param.required,
+                items=tool_param.items,  # Will be None for non-array types
+            )
+        },
+    )
+
+    openai_tool = convert_tooldef_to_openai_tool(tool_def)
+
+    # Verify basic structure
+    assert openai_tool["type"] == "function"
+    parameters = openai_tool["function"]["parameters"]
+    assert "name" in parameters["properties"]
+
+    name_param = parameters["properties"]["name"]
+    assert name_param["type"] == "string"
+    # items should not be present for non-array types
+    assert "items" not in name_param or name_param.get("items") is None
+
+
+def test_mcp_tool_conversion_complex_array_items():
+    """Test array parameter with complex items schema (object type)."""
+    tool_param = ToolParameter(
+        name="configs",
+        parameter_type="array",
+        description="Array of configuration objects",
+        required=False,
+        items={
+            "type": "object",
+            "properties": {
+                "key": {"type": "string"},
+                "value": {"type": "string"},
+            },
+            "required": ["key"],
+        },
+    )
+
+    tool_def = ToolDefinition(
+        tool_name="test_tool",
+        description="Test tool with complex array parameter",
+        parameters={
+            "configs": ToolParamDefinition(
+                param_type=tool_param.parameter_type,
+                description=tool_param.description,
+                required=tool_param.required,
+                items=tool_param.items,
+            )
+        },
+    )
+
+    openai_tool = convert_tooldef_to_openai_tool(tool_def)
+
+    # Verify complex items schema is preserved
+    parameters = openai_tool["function"]["parameters"]
+    configs_param = parameters["properties"]["configs"]
+
+    assert configs_param["type"] == "array"
+    assert "items" in configs_param
+    assert configs_param["items"]["type"] == "object"
+    assert "properties" in configs_param["items"]
+    assert "key" in configs_param["items"]["properties"]
+    assert "value" in configs_param["items"]["properties"]