Support MCP connector in agent update API

[jiapingzeng]

Description

Support MCP connector in agent update API

Related Issues

Resolves #4321

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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---

Scenarios tested:

initial agent parameters:

{
  "_llm_interface": "bedrock/converse/claude",
  "mcp_connectors": "[{\"mcp_connector_id\":\"initial-connector-123\",\"tool_filters\":[\"^get_.*$\"]}]"
}

1. Update connector filters:

PUT /_plugins/_ml/agents/{{agent_id}}
{
    "parameters": {
        "mcp_connectors": [{
            "mcp_connector_id": "updated-connector-456",
            "tool_filters": ["^list_.*$"]
        }]
    }
}

GET /_plugins/_ml/agents/{{agent_id}}
...
{
  "_llm_interface": "bedrock/converse/claude",
  "mcp_connectors": "[{\"mcp_connector_id\":\"updated-connector-456\",\"tool_filters\":[\"^list_.*$\"]}]"
}

2. Remove connector

PUT /_plugins/_ml/agents/{{agent_id}}
{
    "parameters": {
        "mcp_connectors": []
    }
}

GET /_plugins/_ml/agents/{{agent_id}}
...
{
  "_llm_interface": "bedrock/converse/claude",
  "mcp_connectors": "[]"
}

3. Add connector to agent without connector

PUT /_plugins/_ml/agents/{{agent_id}}
{
    "parameters": {
        "mcp_connectors": [{
            "mcp_connector_id": "newly-added-connector-789",
            "tool_filters": ["^search_.*$"]
        }]
    }
}

GET /_plugins/_ml/agents/{{agent_id}}
{
  "_llm_interface": "bedrock/converse/claude",
  "mcp_connectors": "[{\"mcp_connector_id\":\"newly-added-connector-789\",\"tool_filters\":[\"^search_.*$\"]}]"
}

[jiapingzeng]

Test failure is not related to my change:

> Could not GET 'https://ci.opensearch.org/ci/dbc/snapshots/maven/commons-codec/commons-codec/1.19.0/commons-codec-1.19.0.pom'. Received status code 503 from server: Service Unavailable

Will run build locally to verify.

Edit: succeeds locally

[rithin-pullela-aws]

Thanks for the PR JP!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.06%. Comparing base (305cb8e) to head (5d15ce9).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4352      +/-   ##
============================================
- Coverage     80.09%   80.06%   -0.03%     
+ Complexity    10199    10185      -14     
============================================
  Files           855      855              
  Lines         44373    44374       +1     
  Branches       5135     5135              
============================================
- Hits          35539    35529      -10     
- Misses         6670     6680      +10     
- Partials       2164     2165       +1     

Flag	Coverage Δ
ml-commons	80.06% <100.00%> (-0.03%)	⬇️

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