llamaIndex - 💡(How to fix) Fix [Feature Request]: Tool output postprocessing and composable middleware (follow-up from #20386) [1 comments, 2 participants]

TL;DR

Implement a ToolIOMiddleware class to enable composable middleware and hook API for pre/post IO transformations.

Guidance

• Identify the specific requirements for output postprocessing and middleware functionality needed for the MCP billing tool and other tools.
• Design a ToolIOMiddleware class that can handle both before and after transformations, allowing for flexible and reusable middleware configurations.
• Develop a filter_fields function to deterministically filter the output of tools, such as the MCP billing tool, to only include the necessary fields.
• Consider implementing a registry or factory pattern to manage and compose multiple middleware instances.

Example

class ToolIOMiddleware:
    def __init__(self, before=None, after=None):
        self.before = before
        self.after = after

    def __call__(self, tool_name, args, out=None):
        if self.before:
            args = self.before(tool_name, args)
        if out and self.after:
            out = self.after(tool_name, out)
        return args if out is None else out

Notes

The implementation details of the ToolIOMiddleware class and the filter_fields function will depend on the specific requirements and constraints of the project.

Recommendation

Apply workaround by implementing the ToolIOMiddleware class and associated functions to enable composable middleware and hook API for pre/post IO transformations, as this will allow for more flexible and reusable tool configurations.