[adityasingh2400]

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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: OpenAIResponsesLlm drops the keys beside "result" in a tool's dict return #7836

Problem:
_serialize_json_value unwrapped any tool dict with a non-None "result" key and sent only that value as the function_call_output. A tool returning {"result": "found 2 contracts", "contracts": [...], "next_page_token": "abc"} therefore reached the model as just found 2 contracts, and the rest of the data was silently lost.

Solution:
Unwrap only when the keys are exactly {"result"}, which is ADK's wrapper for a non-dict tool return. Any other dict is JSON-encoded whole. This is the same rule AnthropicLlm uses since #7073. Bare {"result": value} returns, MCP content lists and plain strings are serialized as before.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Added to tests/unittests/integrations/openai/test_openai_responses_llm.py:

• test_function_response_unwraps_adk_result_wrapper: {"result": "sunny"} → sunny, and {"result": [1, 2]} → [1, 2]. This behavior is unchanged.
• test_function_response_keeps_keys_beside_result: the full dict round-trips.

# On main (before the fix)
json.decoder.JSONDecodeError: Expecting value   # output was only "found 2 contracts"
1 failed, 1 passed

# With the fix
$ pytest tests/unittests/integrations/openai
227 passed

pre-commit run passes on the changed files, and mypy reports no issues in _openai_responses_llm.py.

Manual End-to-End (E2E) Tests:

I ran a Runner with LlmAgent(model=OpenAIResponsesLlm(model="gpt-5"), tools=[search_contracts]). The function tool returns the dict above. Only the client's responses.create is replaced: it records each request, asks for search_contracts first and answers second. The output below is the function_call_output in the second request:

=== BEFORE (main) ===
function_call_output sent to OpenAI: found 2 contracts
=== AFTER (this PR) ===
function_call_output sent to OpenAI: {"result": "found 2 contracts", "contracts": ["NDA-12", "MSA-7"], "next_page_token": "abc"}

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

None.