fix(gemini): support snake_case for google_search tool parameters

[Chesars]

Relevant issues

Fixes #18171

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

• I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement - see details
• My PR passes all unit tests on make test-unit
• My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🐛 Bug Fix

Changes

Summary

Adds snake_case support for Gemini/Vertex AI tool parameters to align with:

• OpenAI API naming conventions (snake_case for function names)
• PEP 8 Python style guide (snake_case for functions/variables)
• Google's official Gemini API documentation
• Existing LiteLLM patterns (e.g., google_maps, url_context)

When users follow Google's Gemini API documentation and use {"google_search": {}}, the tool parameter is ignored, causing a 400 error. This violates LiteLLM's core principle: "Call all LLM APIs using the OpenAI format".

Solution

Accept both snake_case and camelCase variants for tool names:

• google_search → googleSearch
• google_search_retrieval → googleSearchRetrieval
• enterprise_web_search → enterpriseWebSearch

Maintains backward compatibility - existing googleSearch calls continue to work.

Files Modified

• litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py

  • Updated tool name matching to accept both snake_case and camelCase
  • Follows same pattern as google_maps (line 502-504)

• tests/litellm/llms/vertex_ai/gemini/test_transformation.py

  • Added 4 comprehensive tests covering all tool variants

Users following official Google documentation should not receive errors. LiteLLM's job is to translate Python-style input → provider-native format, not force users to learn provider-specific naming conventions.

Documentation References

• Google's Official Docs:

  • Gemini API - Google Search Tool - uses google_search
  • Vertex AI Python SDK Example - uses Tool(google_search=GoogleSearch())

• Python Standards:

  • PEP 8 - Function and Variable Names - "Function names should be lowercase, with words separated by underscores as necessary to improve readability."

• LiteLLM Design Principle:

  • README - "Call all LLM APIs using the OpenAI (or native) format" & "Translate inputs to provider's completion endpoints"

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Note: This PR reopens the discussion from #18189. The implementation includes the same fixes with additional formatting improvements.

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Project	Deployment	Review	Updated (UTC)
litellm	Ready	Preview, Comment	Dec 26, 2025 10:46pm