dotnet8 Aot ，Errors cannot be resolved even with all efforts

[ccnetcore]

No complex logic was used, just copied examples from GitHub and added some objects
Not using JSON serialization, etc

Unhandled Exception: System.NotSupportedException: JsonTypeInfo metadata for type 'System.Collections.Generic.List`1[AiFileMaster.Server.Tools.FileTools.FileItemInfo]' was not provided by TypeInfoResolver of type '[ModelContextProtocol.McpJsonUtilities+JsonContext, Microsoft.Extensions.AI.AIJsonUtilities+JsonContext]'. If using source generation, ensure that all root types passed to the serializer have been annotated with 'JsonSerializableAttribute', along with any types that might be serialized polymorphically.

I hope someone can solve it

[PederHP]

Can you provide a reproducible? I assume you're using a List as argument or return type from a method, that implements a Tool?

Because you are using JSON serialization then, as MCP builds on JSON-RPC, and under the hood those types need to be handled by the serializer. So you need to do the necessary legwork to make them JsonSerializable.

You could also avoid the complex types - especially if it's for input. Models aren't good with very complex input schemas. And for output schema (the return object) it's actually thrown away by the vast majority of clients - they just get the serialized JSON output - and they never send the output schema to the model (as LLM APIs don't support it natively currently). So you can just return a string or text content object. I know that sounds like a hacky work around - but if you really need the AOT, and you don't control the client, it's a fair workaround. But it's easier to give some qualified input if you have a small code sample.

There's a clean way to fix this as well, of course. Which is to use JsonSerializableAttribute, JsonSerializerContext, etc. to make sure the types work with AOT. But I can see why it feels annoying that it requires that much legwork, but AOT is rarely entirely free effortwise.

[ccnetcore]

Thank you very much for waiting for your reply

I am using the demo provided by the current warehouse
Then a McpServer Tool was added to retrieve file directory information by passing in the path
The returned file is the List, a list object representing the list file
As follows:

[McpServerTool, Description("Retrieve file information")]
public List<FileItemInfo> GetFiles([Description("User provided path")] string path,
[Description("Do you need to organize the subfiles in the folder")] bool includeChildrenFile)

FileItemInfo is my custom class, a simple object