Fix unsupported operation exception in execute tool API

[nathaliellenaa]

Description

There's an issue when executing ReadFromScratchPadTool or WriteToScratchPadTool with empty parameters through the execute tool API. While these tools should support empty parameter execution, they currently throw an exception:

POST /_plugins/_ml/tools/_execute/ReadFromScratchPadTool
{
  "parameters": {}
}

// Exception thrown
{
    "status": 500,
    "error": {
        "type": "NotSerializableExceptionWrapper",
        "reason": "System Error",
        "details": "unsupported_operation_exception: null"
    }
}

The issue is due to the immutable map implementations being passed to these tools. These tools expect to modify the parameters map during execution (reference). When they attempt to call parameters.put() on an immutable map, an UnsupportedOperationException is thrown.

To fix this issue, we need to ensure these tools always receive a mutable map by creating a mutable copy of the parameters before passing them to the tools. This will allow the tools to modify the parameters as needed during execution, even when starting with empty parameters.

Test with current fix:

POST /_plugins/_ml/tools/_execute/ReadFromScratchPadTool
{
  "parameters": {}
}


// Successful response
{
    "inference_results": [
        {
            "output": [
                {
                    "name": "response",
                    "result": "Scratchpad is empty."
                }
            ]
        }
    ]
}

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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[mingshl]

the fix makes sense, because scratch pad string is updated through multiple tool use in one agent execution, so it should be mutable parameters in toolExecution.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.08%. Comparing base (305cb8e) to head (d9f8644).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4325      +/-   ##
============================================
- Coverage     80.09%   80.08%   -0.01%     
+ Complexity    10199    10198       -1     
============================================
  Files           855      855              
  Lines         44373    44374       +1     
  Branches       5135     5135              
============================================
  Hits          35539    35539              
  Misses         6670     6670              
- Partials       2164     2165       +1     

Flag	Coverage Δ
ml-commons	80.08% <100.00%> (-0.01%)	⬇️

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