Fix PydanticUserError

✅ Solution

PydanticUserError often arises in Langchain when Pydantic struggles to automatically infer the correct JSON schema for custom classes used in tool schemas, especially those with complex types or custom validation. To resolve this, explicitly define the `schema` for your custom class using `from pydantic import BaseModel, Field` and leverage Field's `json_schema_extra` argument to provide the necessary schema details. This manual schema definition guides Pydantic and ensures accurate serialization for Langchain functionalities.