.Net: Python: Bug: OpenAPI plugin sends array and boolean query parameters as Python repr (tags=['a', 'b'], active=True) #14788

Describe the bug

The OpenAPI plugin builds the query string with urlencode(segments) and passes argument values through unchanged:

Without doseq=True, urlencode calls str() on each value. So an array query parameter is sent as Python's list repr (['red', 'blue']), and a boolean is sent as True/False. APIs can't parse either. OpenAPI's default for query parameters is style: form, explode: true, which means tags=red&tags=blue and active=true. The .NET OpenAPI plugin already serializes arrays this way.

The schema advertised to the model says {"type": "array", "items": {"type": "string"}}, so a tool call from the model hits this.

Header and path parameters have the same problem, since they use str(argument) (L218, L331).

To Reproduce

semantic-kernel 1.47.0. rest_api_operation.py is the same on main (25bd1bb). This runs offline: httpx.MockTransport captures the request, and the server is an IP literal so the URL validator doesn't need DNS.

import asyncio, httpx
from semantic_kernel import Kernel
from semantic_kernel.connectors.openapi_plugin import OpenAPIFunctionExecutionParameters

spec = {
    "openapi": "3.0.1", "info": {"title": "t", "version": "1"},
    "servers": [{"url": "https://93.184.216.34"}],
    "paths": {"/items": {"get": {
        "operationId": "listItems",
        "parameters": [
            {"name": "tags", "in": "query", "schema": {"type": "array", "items": {"type": "string"}}},
            {"name": "active", "in": "query", "schema": {"type": "boolean"}},
        ],
        "responses": {"200": {"description": "ok"}},
    }}},
}

seen = []
def handler(request):
    seen.append(str(request.url))
    return httpx.Response(200, json={})

async def main():
    client = httpx.AsyncClient(transport=httpx.MockTransport(handler))
    kernel = Kernel()
    plugin = kernel.add_plugin_from_openapi(
        "api", openapi_parsed_spec=spec,
        execution_settings=OpenAPIFunctionExecutionParameters(http_client=client),
    )
    await kernel.invoke(plugin["listItems"], tags=["red", "blue"], active=True)
    print(seen[0])

asyncio.run(main())

Output:

https://93.184.216.34/items?tags=%5B%27red%27%2C+%27blue%27%5D&active=True

Expected behavior

https://93.184.216.34/items?tags=red&tags=blue&active=true

(form/explode, the OpenAPI default for query parameters), with booleans written as JSON true/false.

Platform

• Language: Python
• Source: semantic-kernel 1.47.0 (pip) / main at 25bd1bb
• AI model: n/a (no model call needed)
• IDE: n/a
• OS: Windows 11, Python 3.12

Additional context

The parser doesn't read style/explode from the spec yet (RestApiParameter is always built without them), so the smallest fix is to serialize lists as repeated keys (doseq=True) and booleans as lowercase. Happy to send a fix if that helps.