fix(llm) - Fix Raw Schema for Google Gemini

[fgoessl]

Bug Description

Function tools work correctly with Google Gemini if they are declared using the @function_tool decorator.

If they are supplied as a Raw Schema however, only the tool name and the tool description are visible to the model and the parameters are empty. As a result the tool cannot be properly used by the model.

Steps to Reproduce

1. Define a tool using a raw schema as described here https://docs.livekit.io/agents/logic/tools/definition/#creating-tools-from-raw-schema.
2. Use: livekit-agents==1.5.2 and gemini-live-2.5-flash-native-audio.
3. Observe the tool calls and/or directly ask the model on what tools it has access to and what parameters they have.

Expected Behavior

The parameters are available to the model. The behaviour of decorated tools and tools generated from raw schemata should match.

Actual Behaviour

Only the tool name and description are available to the model.

I would be happy to add some tests if needed. Just let me know how they are handled here.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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