MCP tools turn upstream HTTP errors into AgentsException, crashing the run

[Manouchehri]

Description

If an MCP tool call receives a non-2xx response from its upstream service, the wrapper raises an AgentsException. Because the tool never returns a result object, the agent cannot handle the failure and the entire turn aborts.

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Steps to Reproduce

1. Invoke any MCP tool with parameters that make the upstream API reply with an error (e.g., an invalid search query).
2. Observe that the run terminates with an uncaught AgentsException.

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Expected Result

The tool returns a structured error payload so the agent can decide how to respond.

Actual Result

An AgentsException is raised and the run stops.

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Sanitized Traceback

Error invoking MCP tool <tool_name>: GET <service-url>?q=<masked_query>: 422 <service-error>

Traceback (most recent call last):
  File "<site-packages>/agents/mcp/util.py", line 104, in invoke_mcp_tool
    result = await server.call_tool(tool.name, json_data)
  ...
mcp.shared.exceptions.McpError: GET <service-url>: 422 <service-error>
agents.exceptions.AgentsException: Error invoking MCP tool <tool_name>: ...