Python: Fix schema handling. Fix function result return for type list. (

#6370)

### Motivation and Context

Building the tools json payload from the kernel parameter metadata
wasn't properly including an object of type `array`.

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### Description

Correctly include the object type `array` so that the tool call doesn't
return a bad request. Add unit tests.
- Closes #6367 
- Closes #6360
- Fixes the FunctionResult return for a type string -- if the
FunctionResult is of type KernelContent then return the first element of
the list, otherwise return the complete list.
- Fix the kernel function from method to include the proper type_object
for the return parameter so that the schema can be created properly.
- Add retry logic for a sometimes flaky function calling stepwise
planner integration test.
- Add a check during function calling that makes sure the model is
returning the proper number of arguments based on how many function
arguments are required.

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [X] The code builds clean without any errors or warnings
- [X] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [X] All unit tests pass, and I have added new tests where possible
- [X] I didn't break anyone 😄

python/semantic_kernel/connectors/ai/open_ai/services/open_ai_chat_completion_base.py

@@ -474,6 +474,22 @@ async def _process_function_call(
             chat_history.add_message(message=frc.to_chat_message_content())
             return
 
+        num_required_func_params = len([param for param in function_to_call.parameters if param.is_required])
+        if len(parsed_args) < num_required_func_params:
+            msg = (
+                f"There are `{num_required_func_params}` tool call arguments required and "
+                f"only `{len(parsed_args)}` received. The required arguments are: "
+                f"{[param.name for param in function_to_call.parameters if param.is_required]}. "
+                "Please provide the required arguments and try again."
+            )
+            logger.exception(msg)
+            frc = FunctionResultContent.from_function_call_content_and_result(
+                function_call_content=function_call,
+                result=msg,
+            )
+            chat_history.add_message(message=frc.to_chat_message_content())
+            return
+
         _rebuild_auto_function_invocation_context()
         invocation_context = AutoFunctionInvocationContext(
             function=function_to_call,

python/semantic_kernel/connectors/ai/open_ai/services/utils.py

@@ -37,19 +37,30 @@ def kernel_function_metadata_to_openai_tool_format(metadata: KernelFunctionMetad
 
     def parse_schema(schema_data):
         """Recursively parse the schema data to include nested properties."""
-        if schema_data.get("type") == "object":
+        if schema_data is None:
+            return {"type": "string", "description": ""}
+
+        schema_type = schema_data.get("type")
+        schema_description = schema_data.get("description", "")
+
+        if schema_type == "object":
+            properties = {key: parse_schema(value) for key, value in schema_data.get("properties", {}).items()}
             return {
                 "type": "object",
-                "properties": {key: parse_schema(value) for key, value in schema_data.get("properties", {}).items()},
-                "description": schema_data.get("description", ""),
-            }
-        else:
-            return {
-                "type": schema_data.get("type", "string"),
-                "description": schema_data.get("description", ""),
-                **({"enum": schema_data.get("enum")} if "enum" in schema_data else {}),
+                "properties": properties,
+                "description": schema_description,
             }
 
+        if schema_type == "array":
+            items = schema_data.get("items", {"type": "string"})
+            return {"type": "array", "description": schema_description, "items": items}
+
+        schema_dict = {"type": schema_type, "description": schema_description}
+        if "enum" in schema_data:
+            schema_dict["enum"] = schema_data["enum"]
+
+        return schema_dict
+
     return {
         "type": "function",
         "function": {

python/semantic_kernel/connectors/openapi_plugin/models/rest_api_operation.py

@@ -0,0 +1,275 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+import re
+from typing import Any
+from urllib.parse import urlencode, urljoin, urlparse, urlunparse
+
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_expected_response import (
+    RestApiOperationExpectedResponse,
+)
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_parameter import RestApiOperationParameter
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_parameter_location import (
+    RestApiOperationParameterLocation,
+)
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_parameter_style import (
+    RestApiOperationParameterStyle,
+)
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_payload import RestApiOperationPayload
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_payload_property import (
+    RestApiOperationPayloadProperty,
+)
+from semantic_kernel.exceptions.function_exceptions import FunctionExecutionException
+from semantic_kernel.functions.kernel_parameter_metadata import KernelParameterMetadata
+from semantic_kernel.utils.experimental_decorator import experimental_class
+
+
+@experimental_class
+class RestApiOperation:
+    MEDIA_TYPE_TEXT_PLAIN = "text/plain"
+    PAYLOAD_ARGUMENT_NAME = "payload"
+    CONTENT_TYPE_ARGUMENT_NAME = "content-type"
+    INVALID_SYMBOLS_REGEX = re.compile(r"[^0-9A-Za-z_]+")
+
+    _preferred_responses: list[str] = [
+        "200",
+        "201",
+        "202",
+        "203",
+        "204",
+        "205",
+        "206",
+        "207",
+        "208",
+        "226",
+        "2XX",
+        "default",
+    ]
+
+    def __init__(
+        self,
+        id: str,
+        method: str,
+        server_url: str,
+        path: str,
+        summary: str | None = None,
+        description: str | None = None,
+        params: list["RestApiOperationParameter"] | None = None,
+        request_body: "RestApiOperationPayload | None" = None,
+        responses: dict[str, "RestApiOperationExpectedResponse"] | None = None,
+    ):
+        self.id = id
+        self.method = method.upper()
+        self.server_url = server_url
+        self.path = path
+        self.summary = summary
+        self.description = description
+        self.parameters = params
+        self.request_body = request_body
+        self.responses = responses
+
+    def url_join(self, base_url: str, path: str):
+        """Join a base URL and a path, correcting for any missing slashes."""
+        parsed_base = urlparse(base_url)
+        if not parsed_base.path.endswith("/"):
+            base_path = parsed_base.path + "/"
+        else:
+            base_path = parsed_base.path
+        full_path = urljoin(base_path, path.lstrip("/"))
+        return urlunparse(parsed_base._replace(path=full_path))
+
+    def build_headers(self, arguments: dict[str, Any]) -> dict[str, str]:
+        headers = {}
+
+        parameters = [p for p in self.parameters if p.location == RestApiOperationParameterLocation.HEADER]
+
+        for parameter in parameters:
+            argument = arguments.get(parameter.name)
+
+            if argument is None:
+                if parameter.is_required:
+                    raise FunctionExecutionException(
+                        f"No argument is provided for the `{parameter.name}` "
+                        f"required parameter of the operation - `{self.id}`."
+                    )
+                continue
+
+            headers[parameter.name] = str(argument)
+
+        return headers
+
+    def build_operation_url(self, arguments, server_url_override=None, api_host_url=None):
+        server_url = self.get_server_url(server_url_override, api_host_url)
+        path = self.build_path(self.path, arguments)
+        return urljoin(server_url.geturl(), path.lstrip("/"))
+
+    def get_server_url(self, server_url_override=None, api_host_url=None):
+        if server_url_override is not None and server_url_override.geturl() != b"":
+            server_url_string = server_url_override.geturl()
+        else:
+            server_url_string = (
+                self.server_url.geturl()
+                if self.server_url
+                else api_host_url.geturl() if api_host_url else self._raise_invalid_operation_exception()
+            )
+
+        # make sure the base URL ends with a trailing slash
+        if not server_url_string.endswith("/"):
+            server_url_string += "/"
+
+        return urlparse(server_url_string)
+
+    def build_path(self, path_template: str, arguments: dict[str, Any]) -> str:
+        parameters = [p for p in self.parameters if p.location == RestApiOperationParameterLocation.PATH]
+        for parameter in parameters:
+            argument = arguments.get(parameter.name)
+            if argument is None:
+                if parameter.is_required:
+                    raise FunctionExecutionException(
+                        f"No argument is provided for the `{parameter.name}` "
+                        f"required parameter of the operation - `{self.id}`."
+                    )
+                continue
+            path_template = path_template.replace(f"{{{parameter.name}}}", str(argument))
+        return path_template
+
+    def build_query_string(self, arguments: dict[str, Any]) -> str:
+        segments = []
+        parameters = [p for p in self.parameters if p.location == RestApiOperationParameterLocation.QUERY]
+        for parameter in parameters:
+            argument = arguments.get(parameter.name)
+            if argument is None:
+                if parameter.is_required:
+                    raise FunctionExecutionException(
+                        f"No argument or value is provided for the `{parameter.name}` "
+                        f"required parameter of the operation - `{self.id}`."
+                    )
+                continue
+            segments.append((parameter.name, argument))
+        return urlencode(segments)
+
+    def replace_invalid_symbols(self, parameter_name):
+        return RestApiOperation.INVALID_SYMBOLS_REGEX.sub("_", parameter_name)
+
+    def get_parameters(
+        self,
+        operation: "RestApiOperation",
+        add_payload_params_from_metadata: bool = True,
+        enable_payload_spacing: bool = False,
+    ) -> list["RestApiOperationParameter"]:
+        params = list(operation.parameters)
+        if operation.request_body is not None:
+            params.extend(
+                self.get_payload_parameters(
+                    operation=operation,
+                    use_parameters_from_metadata=add_payload_params_from_metadata,
+                    enable_namespacing=enable_payload_spacing,
+                )
+            )
+
+        for parameter in params:
+            parameter.alternative_name = self.replace_invalid_symbols(parameter.name)
+
+        return params
+
+    def create_payload_artificial_parameter(self, operation: "RestApiOperation") -> "RestApiOperationParameter":
+        return RestApiOperationParameter(
+            name=self.PAYLOAD_ARGUMENT_NAME,
+            type=(
+                "string"
+                if operation.request_body
+                and operation.request_body.media_type == RestApiOperation.MEDIA_TYPE_TEXT_PLAIN
+                else "object"
+            ),
+            is_required=True,
+            location=RestApiOperationParameterLocation.BODY,
+            style=RestApiOperationParameterStyle.SIMPLE,
+            description=operation.request_body.description if operation.request_body else "REST API request body.",
+            schema=operation.request_body.schema if operation.request_body else None,
+        )
+
+    def create_content_type_artificial_parameter(self) -> "RestApiOperationParameter":
+        return RestApiOperationParameter(
+            name=self.CONTENT_TYPE_ARGUMENT_NAME,
+            type="string",
+            is_required=False,
+            location=RestApiOperationParameterLocation.BODY,
+            style=RestApiOperationParameterStyle.SIMPLE,
+            description="Content type of REST API request body.",
+        )
+
+    def _get_property_name(
+        self, property: RestApiOperationPayloadProperty, root_property_name: bool, enable_namespacing: bool
+    ):
+        if enable_namespacing and root_property_name:
+            return f"{root_property_name}.{property.name}"
+        return property.name
+
+    def _get_parameters_from_payload_metadata(
+        self,
+        properties: list["RestApiOperationPayloadProperty"],
+        enable_namespacing: bool = False,
+        root_property_name: bool = None,
+    ) -> list["RestApiOperationParameter"]:
+        parameters: list[RestApiOperationParameter] = []
+        for property in properties:
+            parameter_name = self._get_property_name(property, root_property_name, enable_namespacing)
+            if not property.properties:
+                parameters.append(
+                    RestApiOperationParameter(
+                        name=parameter_name,
+                        type=property.type,
+                        is_required=property.is_required,
+                        location=RestApiOperationParameterLocation.BODY,
+                        style=RestApiOperationParameterStyle.SIMPLE,
+                        description=property.description,
+                        schema=property.schema,
+                    )
+                )
+            parameters.extend(
+                self._get_parameters_from_payload_metadata(property.properties, enable_namespacing, parameter_name)
+            )
+        return parameters
+
+    def get_payload_parameters(
+        self, operation: "RestApiOperation", use_parameters_from_metadata: bool, enable_namespacing: bool
+    ):
+        if use_parameters_from_metadata:
+            if operation.request_body is None:
+                raise Exception(
+                    f"Payload parameters cannot be retrieved from the `{operation.Id}` "
+                    f"operation payload metadata because it is missing."
+                )
+            if operation.request_body.media_type == RestApiOperation.MEDIA_TYPE_TEXT_PLAIN:
+                return [self.create_payload_artificial_parameter(operation)]
+
+            return self._get_parameters_from_payload_metadata(operation.request_body.properties, enable_namespacing)
+
+        return [
+            self.create_payload_artificial_parameter(operation),
+            self.create_content_type_artificial_parameter(operation),
+        ]
+
+    def get_default_response(
+        self, responses: dict[str, RestApiOperationExpectedResponse], preferred_responses: list[str]
+    ) -> RestApiOperationExpectedResponse | None:
+        for code in preferred_responses:
+            if code in responses:
+                return responses[code]
+        # If no appropriate response is found, return None
+        return None
+
+    def get_default_return_parameter(self, preferred_responses: list[str] | None = None) -> KernelParameterMetadata:
+        if preferred_responses is None:
+            preferred_responses = self._preferred_responses
+
+        rest_operation_response = self.get_default_response(self.responses, preferred_responses)
+
+        if rest_operation_response:
+            return KernelParameterMetadata(
+                name="return",
+                description=rest_operation_response.description,
+                type_=rest_operation_response.schema.get("type") if rest_operation_response.schema else None,
+                schema_data=rest_operation_response.schema,
+            )
+
+        return None

python/semantic_kernel/connectors/openapi_plugin/models/rest_api_operation_expected_response.py

@@ -0,0 +1,12 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+
+from semantic_kernel.utils.experimental_decorator import experimental_class
+
+
+@experimental_class
+class RestApiOperationExpectedResponse:
+    def __init__(self, description: str, media_type: str, schema: str | None = None):
+        self.description = description
+        self.media_type = media_type
+        self.schema = schema

python/semantic_kernel/connectors/openapi_plugin/models/rest_api_operation_parameter.py

@@ -0,0 +1,41 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+from typing import Any
+
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_expected_response import (
+    RestApiOperationExpectedResponse,
+)
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_parameter_location import (
+    RestApiOperationParameterLocation,
+)
+from semantic_kernel.connectors.openapi_plugin.models.rest_api_operation_parameter_style import (
+    RestApiOperationParameterStyle,
+)
+from semantic_kernel.utils.experimental_decorator import experimental_class
+
+
+@experimental_class
+class RestApiOperationParameter:
+    def __init__(
+        self,
+        name: str,
+        type: str,
+        location: RestApiOperationParameterLocation,
+        style: RestApiOperationParameterStyle | None = None,
+        alternative_name: str | None = None,
+        description: str | None = None,
+        is_required: bool = False,
+        default_value: Any | None = None,
+        schema: str | None = None,
+        response: RestApiOperationExpectedResponse | None = None,
+    ):
+        self.name = name
+        self.type = type
+        self.location = location
+        self.style = style
+        self.alternative_name = alternative_name
+        self.description = description
+        self.is_required = is_required
+        self.default_value = default_value
+        self.schema = schema
+        self.response = response