Tool call fails in ADK

[shivsant]

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Describe the bug
Getting error when using OpenAI GPT4O with ADK (Multi Agent, agent delegation, tool call)

HTTP 400 (invalid_request_error: )
Parameter: messages.[7].role

Invalid parameter: messages with role 'tool' must be a response to a preceeding message with 'tool_calls'.

To Reproduce
If I have bunch of steps to do, I am seeing this.
This is not always reproducible. Trying to see if someone has seen this.

Desktop (please complete the following information):

• OS: SLES15-SP4
• Python version(python -V): 3.11.1
• ADK version(pip show google-adk): 1.1.1