improve error handling

Signed-off-by: Prashant <prashant.rakheja@sap.com>

Author: prashantrakheja

src/sap_cloud_sdk/agentgateway/agw_client.py

@@ -171,7 +171,8 @@ async def list_mcp_tools(
             raise
         except Exception as e:
             logger.exception("Unexpected error during tool discovery")
-            raise AgentGatewaySDKError(f"Tool discovery failed: {e}") from e
+            cause = _unwrap_exception_group(e)
+            raise AgentGatewaySDKError(f"Tool discovery failed: {cause}") from e
 
     @record_metrics(Module.AGENTGATEWAY, Operation.AGENTGATEWAY_CALL_MCP_TOOL)
     async def call_mcp_tool(
@@ -264,11 +265,19 @@ async def call_mcp_tool(
             raise
         except Exception as e:
             logger.exception("Unexpected error during tool invocation")
+            cause = _unwrap_exception_group(e)
             raise AgentGatewaySDKError(
-                f"Tool invocation failed for '{tool.name}': {e}"
+                f"Tool invocation failed for '{tool.name}': {cause}"
             ) from e
 
 
+def _unwrap_exception_group(exc: Exception) -> Exception:
+    """Unwrap nested ExceptionGroups to present meaningful error messages."""
+    while isinstance(exc, BaseExceptionGroup) and exc.exceptions:
+        exc = exc.exceptions[0]
+    return exc
+
+
 def create_client(
     tenant_subdomain: str | Callable[[], str] | None = None,
     timeout: float = 60.0,