ToolMethodInvoker loses generic type information for List<T> parameters

[richuV]

Description

When a tool method has a parameter with a generic type like List<MyClass>, the ToolMethodInvoker.convertSingleParameter method fails to properly deserialize it, resulting in a ClassCastException:

java.util.LinkedHashMap cannot be cast to class MyClass
(java.util.LinkedHashMap is in module java.base of loader 'bootstrap';
MyClass is in unnamed module of loader 'app')

Root Cause

In ToolMethodInvoker.java line 298:

Class<?> paramType = parameter.getType();

This only returns the raw type (List.class) and loses the generic type argument (<MyClass>).

When Jackson's convertValue(value, List.class) is called, it doesn't know the element type and defaults to LinkedHashMap.

Reproduction

public class MyTool {
    @Tool(name = my_tool, description = ...)
    public ToolResultBlock doSomething(
            @ToolParam(name = items) List<MyItem> items) {
        // ClassCastException when iterating items
        for (MyItem item : items) { ... }
    }
}

Suggested Fix

Use parameter.getParameterizedType() instead of parameter.getType() to preserve generic type information:

private Object convertSingleParameter(Parameter parameter, Map<String, Object> input) {
    // ... existing code ...

    Type paramType = parameter.getParameterizedType();  // Changed from getType()

    // Handle generic types
    if (paramType instanceof ParameterizedType) {
        JavaType javaType = mapper.getTypeFactory().constructType(paramType);
        return mapper.convertValue(value, javaType);
    }

    // Fallback for non-generic types
    return JsonUtils.getJsonCodec().convertValue(value, parameter.getType());
}

Alternatively, add a new method to JsonCodec interface:

<T> T convertValue(Object from, Type type);

Workaround

Currently, users can work around this by:

1. Using Object as parameter type and manually converting with TypeReference
2. Creating a wrapper class instead of using List<T> directly

Environment

• agentscope-java version: latest main branch
• Java version: 21