.NET: Foundry Agent - MCP fails server side. No error propagated to client

[graemefoster]

Hi,

On Agent Framework version: 1.0.0-preview.251016.1

I referenced an MCP server in a Foundry Agent. The Foundry Agent fails when I run the thread.

I can see the following message in Fiddler:

event: thread.run.failed
data: {
  "id": "run_AptSDFasdasddasd",
  "object": "thread.run",
  "created_at": 1761180339,
  "assistant_id": "asst_asdasdasd",
  "thread_id": "thread_asdasdas",
  "status": "failed",
  "started_at": 1761180340,
  "expires_at": null,
  "cancelled_at": null,
  "failed_at": 1761180340,
  "completed_at": null,
  "required_action": null,
  "last_error": {
    "code": "tool_server_error",
    "message": "Error: list_tools_server_error; Server error while listing tools: Failed to enumerate tools from remote server: https://8e5c3d750dc4.ngrok-free.app:443/. Response status code does not indicate success: 405 (Method Not Allowed)."
  },
  "tools": [
    {
      "type": "mcp",
      "server_label": "WeatherMcp",
      "server_url": "https://sdfasdasdadasdaddas.ngrok-free.app",
      "allowed_tools": null
    }
  ],
 ...
}

A call to await agent.RunAsync completes successfully, with an empty string in the Agent Message.

Would expect an exception, or something to indicate the failure in the RunAsync response.

[tonybaloney]

Python has the same issue. All of my MCP calls timed out (the endpoint was broken) but instead of erroring the workflow, it continued and hallucinated the output.

[rogerbarreto]

The root cause of this issue is related to the

• .NET: Investigate PersistentChatClient Swallowing errors related to incorrect tool setting. #714

which was recently addressed, I'm closing this issue as resolved and the fix should be available as soon a new release of Azure.AI.Agents.Persistent package is included in MAF next release.