Validation response for invalid request - WrapBusinessError vs JsonRPC

[sabob]

Hi all,

When using Jakarta Validation on a tool method parameter, the response differs based on the presence of @WrapBusinessError.

Example:

@Tool
foo(FooRequest request)

class FooRequest {
    @NotBlank
    private String sessionId;
}

With @WrapBusinessError:

{
  "content": [
    {
      "type": "text",
      "text": "io.quarkiverse.mcp.server.McpException: chat.request.sessionId: must not be blank"
    }
  ],
  "isError": true
}

Without @WrapBusinessError:

{
  "error": "MCP error -32602: chat.request.sessionId: must not be blank"
}

I've also included the (MCP Server - Hibernate Validator dependency.

Is this expected response?

Is the 2nd response viewed as a Protocol error and with @WrapBusinessError is a Tool error?

Kind regards

Bob

[mkouba]

Yes, that's expected. @WrapBusinessError with default config basically means - catch any exception thrown and wrap it with a ToolCallException, i.e. produce a business logic error and return a tool response with isError=true.

You can change the WrapBusinessError#value() to change the default behavior.

[sabob]

The reason I use @WrapBusinessError is that any unhandled exceptions are wrapped as business errors. Maybe this is not best practice?

But if the request parameter to my method is invalid, it counts as a protocol error hence the Hibernate Validator Extension returns the json/rpc code:
MCP error -32602: chat.request.sessionId: must not be blank"

Adding WrapBusinessError, turns the protocol level errors into business errors.

Should it not be that WrapBusinessError ignore MCPExceptions, which are protocol errors?

Also, WrapBusinessError#value() can only include specific exceptions but not exclude eg MCPException.

Hope I'm making sense.