MCP tool results should set `is_error: true` when validation fails

[sicoyle]

Describe the bug

When a tool fails due to validation (ex: missing required parameter owner), the response should indicate an error and set is_error: true or the proper error structure. Currently, is_error gets set to false with error text in content. This means that downstream clients are not able to treat this as a failure, so in my case my Dapr Agent is not able to properly handle this failure.

additional context: dapr/dapr-agents#423

Affected version

Remote MCP server endpoint: https://api.githubcopilot.com/mcp/.

Steps to reproduce the behavior

You can reproduce the issue by running my release note agent:
https://github.com/sicoyle/release-note-agent

Expected vs actual behavior

I should be able to parse the error field appropriately in Dapr Agents repo.

Logs

lResult'>)
GithubGetReleaseByTag(tool) (Id: call_eECqd2eObRNweLdG2AHHfMTZ):
{"meta": null, "content": [{"type": "text", "text": "missing required parameter: owner", "annotations": null, "meta": null}], "structured_content": null, "is_error": false}

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[almaleksia]

Thanks for the report, we're going to address it.

[almaleksia]

Hi, I cannot reproduce it anymore. We've made some changes to validation handling recently which probably fixed it. Would be great if you can verify this doesn't happen or keep happening.

[sicoyle]

Hi, I cannot reproduce it anymore. We've made some changes to validation handling recently which probably fixed it. Would be great if you can verify this doesn't happen or keep happening.

Give me a few days pls and I'll get back to you here and let you know :)