feat: configure similarity top-K in the VertexAiRagRetrieval tool

[pgentile]

Link to Issue or Description of Change

Problem:

Add support for the similarity top-K parameter in the VertexAiRagRetrieval tool

Solution:

New similarityTopK constructor parameter in the constructor of the VertexAiRagRetrieval class.

The similarity top-K is then added to the LLM request, when the model is a Gemini one and when the GOOGLE_GENAI_USE_VERTEXAI env var is enabled. Otherwise, the similarity top-K parameter is transmitted to the retrieveContexts method.

Testing Plan

Updates of the VertexAiRagRetrievalTest unit test.

Unit Tests:

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

[INFO] +-- com.google.adk.tools.retrieval.VertexAiRagRetrievalTest
[INFO] | +-- [OK] processLlmRequest_otherModel_doNotAddVertexRagStoreToConfig - 1.298 ss
[INFO] | +-- [OK] processLlmRequest_gemini2Model_addVertexRagStoreToConfig - 0.006 ss

...

[INFO] +-- com.google.adk.tools.retrieval.VertexAiRagRetrievalTest
[INFO] | +-- [OK] processLlmRequest_otherModel_doNotAddVertexRagStoreToConfig - 0.084 ss
[INFO] | +-- [OK] processLlmRequest_gemini2Model_addVertexRagStoreToConfig - 0.001 ss
[INFO] | +-- [OK] runAsync_withResults_returnsContexts - 0.190 ss
[INFO] | +-- [OK] runAsync_noResults_returnsNoResultFoundMessage - 0.003 ss
[INFO] | +-- [OK] processLlmRequest_gemini2Model_withoutSimilarityTopK_addVertexRagStoreToConfig - 0 ss

Manual End-to-End (E2E) Tests:

• Use the tool new parameter in a production agent.
• Check both code branches based on the GOOGLE_GENAI_USE_VERTEXAI env var.
• Count retrieved chunks from the RAG corpus. The number of chunks must match the configured similarity top-K

Checklist

• I have read the CONTRIBUTING.md document.
• My pull request contains a single commit.
• 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

N/A

[hemasekhar-p]

Hi @pgentile, thank you for your contribution! We appreciate you taking the time to submit this pull request. Currently this PR is under review by our team we will keep you posted if any additional information is required. thank you.

[pgentile]

Hi @hemasekhar-p,

Do you know when this PR will be reviewed?

The configuration of this parameter is already available in the Python and Kotlin SDKs.
Having this knob is very useful to get better accuracy of results when I use the RAG Engine.

Thanks

[pgentile2]

Hi @damianmomotgoogle,

I've addressed your review feedback and pushed the fixes.

Thanks 🙏

[damianmomotgoogle]

Thx! Can you squash all commits into a single one with conventional commits message ?

[pgentile]

The commits are now squashed.
I've rebased the PR too.