fix: add prompt field in RAGTool

[SuZhou-Joe]

Description

[Describe what this change achieves]

Issues Resolved

#132

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (7e4c8d5) 80.83% compared to head (23a2502) 80.85%.

Files	Patch %	Lines
.../main/java/org/opensearch/agent/tools/RAGTool.java	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #130      +/-   ##
============================================
+ Coverage     80.83%   80.85%   +0.01%     
- Complexity      195      196       +1     
============================================
  Files            13       13              
  Lines          1002     1008       +6     
  Branches        133      134       +1     
============================================
+ Hits            810      815       +5     
  Misses          141      141              
- Partials         51       52       +1     

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[xinyual]

So will we have a default prompt for RAG tool?

[SuZhou-Joe]

#132

[mingshl]

So will we have a default prompt for RAG tool?

if the prompt is going to add in when register a tool, we should either check if empty prompt then throw exception, or give the prompt a default.

[mingshl]

if (prompt.trim().isEmpty() || prompt == null) {
     throw new IllegalArgumentException("prompt cannot be empty");
}

[zhichao-aws]

Can we set a default prompt for claude model? like #125

[SuZhou-Joe]

So will we have a default prompt for RAG tool?

I once heard that we should never put prompt in our code, it should be a config from user. Will add a validation in Tool.

[SuZhou-Joe]

Based on discussion with @mingshl , we decide to add a validation on prompt field instead of adding a default prompt as the prompt may contain claude-specific template like: Human: turn, which will introduce confusion here.
@mingshl @xinyual @zhichao-aws Could you please help to review and get it merged?

[mingshl]

Hi @SuZhou-Joe ,

IMO, it's better the the prompt should be carried through the tool id, not the RAGTool interface. so I took a look at MLModelTool which is similar to RAGTool that takes a prompt when register the tool and ask llm model a question in a request, MLModelTool doesn't need the prompt in the constructor, the prompt should added through LLMSpec and then in every MLPredictionTaskRequest, it will carry the prompt to use in model prediction.

based on the previous testing on ml-commons feature branch, the RAGToold without the prompt in the constructor was working, I would like to double check if the setting of the RAGTool might lead to issue #132

[xinyual]

So will we have a default prompt for RAG tool?

if the prompt is going to add in when register a tool, we should either check if empty prompt then throw exception, or give the prompt a default.

Yes. I think we could add a default prompt if the prompt is empty like #125