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Propagate tool call exceptions through filters (#844)

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* Add McpProtocolException specifically for JSON-RPC errors
This commit is contained in:
Stephen Halter 2025-10-14 21:10:55 -05:00 • committed by GitHub
commit 3255adb4d6
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1 changed files with 334 additions and 163 deletions
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104
tests/ModelContextProtocol.Tests/Server/McpServerTests.cs
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@ -532,6 +532,110 @@ public class McpServerTests : LoggedTest
await Succeeds_Even_If_No_Handler_Assigned(new ServerCapabilities { Tools = new() }, RequestMethods.ToolsCall, "CallTool handler not configured");
}
[Fact]
public async Task Can_Handle_Call_Tool_Requests_With_McpException()
{
const string errorMessage = "Tool execution failed with detailed error";
await Can_Handle_Requests(
new ServerCapabilities
{
Tools = new()
},
method: RequestMethods.ToolsCall,
configureOptions: options =>
{
options.Handlers.CallToolHandler = async (request, ct) =>
{
throw new McpException(errorMessage);
};
options.Handlers.ListToolsHandler = (request, ct) => throw new NotImplementedException();
},
assertResult: (_, response) =>
{
var result = JsonSerializer.Deserialize<CallToolResult>(response, McpJsonUtilities.DefaultOptions);
Assert.NotNull(result);
Assert.True(result.IsError);
Assert.NotEmpty(result.Content);
var textContent = Assert.IsType<TextContentBlock>(result.Content[0]);
Assert.Contains(errorMessage, textContent.Text);
});
}
[Fact]
public async Task Can_Handle_Call_Tool_Requests_With_Plain_Exception()
{
await Can_Handle_Requests(
new ServerCapabilities
{
Tools = new()
},
method: RequestMethods.ToolsCall,
configureOptions: options =>
{
options.Handlers.CallToolHandler = async (request, ct) =>
{
throw new InvalidOperationException("This sensitive message should not be exposed");
};
options.Handlers.ListToolsHandler = (request, ct) => throw new NotImplementedException();
},
assertResult: (_, response) =>
{
var result = JsonSerializer.Deserialize<CallToolResult>(response, McpJsonUtilities.DefaultOptions);
Assert.NotNull(result);
Assert.True(result.IsError);
Assert.NotEmpty(result.Content);
var textContent = Assert.IsType<TextContentBlock>(result.Content[0]);
// Should be a generic error message, not the actual exception message
Assert.DoesNotContain("sensitive", textContent.Text, StringComparison.OrdinalIgnoreCase);
Assert.Contains("An error occurred", textContent.Text);
});
}
[Fact]
public async Task Can_Handle_Call_Tool_Requests_With_McpProtocolException()
{
const string errorMessage = "Invalid tool parameters";
const McpErrorCode errorCode = McpErrorCode.InvalidParams;
await using var transport = new TestServerTransport();
var options = CreateOptions(new ServerCapabilities { Tools = new() });
options.Handlers.CallToolHandler = async (request, ct) =>
{
throw new McpProtocolException(errorMessage, errorCode);
};
options.Handlers.ListToolsHandler = (request, ct) => throw new NotImplementedException();
await using var server = McpServer.Create(transport, options, LoggerFactory);
var runTask = server.RunAsync(TestContext.Current.CancellationToken);
var receivedMessage = new TaskCompletionSource<JsonRpcError>();
transport.OnMessageSent = (message) =>
{
if (message is JsonRpcError error && error.Id.ToString() == "55")
receivedMessage.SetResult(error);
};
await transport.SendMessageAsync(
new JsonRpcRequest
{
Method = RequestMethods.ToolsCall,
Id = new RequestId(55)
},
TestContext.Current.CancellationToken
);
var error = await receivedMessage.Task.WaitAsync(TimeSpan.FromSeconds(5), TestContext.Current.CancellationToken);
Assert.NotNull(error);
Assert.NotNull(error.Error);
Assert.Equal((int)errorCode, error.Error.Code);
Assert.Equal(errorMessage, error.Error.Message);
await transport.DisposeAsync();
await runTask;
}
private async Task Can_Handle_Requests(ServerCapabilities? serverCapabilities, string method, Action<McpServerOptions>? configureOptions, Action<McpServer, JsonNode?> assertResult)
{
await using var transport = new TestServerTransport();