Tool output formatting should be configurable

[jessedhillon]

Checked

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Feature request

In 'Tool.runyou have a step where a module-local function_format_outputis called on the return value of the tool, which invokes the python builtin functionjson.dumps` on the output. I suggest two improvements:

• take a serializer function option which allows callers to specify their own alternative to json.dumps
• make the entire output formatting stage configurable or overridable through inheritance, rather than strictly calling _format_output

Motivation

We bind tools to the model which are functions that we also use in other parts of our codebase. These functions return Pydantic models, and we have a JSON serializer which automatically dumps these objects to our preferred format. Your formatter is instead sending these objects as the output of their repr. We currently monkey-patch langchain_core.tools.base and replace the json symbol with our own encoder.

Proposal (If applicable)

No response