feat: adding typing to melleatools

[akihikokuroda]

Misc PR

Type of PR

• Bug Fix
• New Feature
• Documentation
• Other

Description

• Link to Issue: fix: feat: investigate adding typing to MelleaTools #541

mellea/backends/tools.py

• Generic type parameters: Introduced ParamSpec (P) and TypeVar (R) to represent tool parameter specifications and return types
• MelleaTool class: Made generic as MelleaTool[P, R] to track callable signatures end-to-end
• Type-safe run() method: Updated signature from run(self, *args: Any, **kwargs: Any) -> Any to run(self, *args: P.args, **kwargs: P.kwargs) -> R,
  preserving caller type information
• Factory methods: Updated from_callable(), from_langchain(), and from_smolagents() return types to MelleaTool[P, R] (or MelleaTool[P, Any] where
  type info is unavailable)
• Decorator overloads: Enhanced @tool decorator overloads to preserve parameter and return types through the entire decoration chain
• Docstrings: Added detailed type parameter documentation and improved examples showing IDE type hints in action

mellea/core/base.py

• AbstractMelleaTool base class: Made generic as AbstractMelleaTool[P, R] with Generic[P, R]
• Abstract run() method: Updated signature to use P.args, P.kwargs, and return type R
• Type parameter documentation: Added Type parameters: section to class docstring explaining P and R
• Import additions: Added ParamSpec to imports for type specification

Testing

• Tests added to the respective file if code was changed
• New code has 100% coverage if code as added
• Ensure existing tests and github automation passes (a maintainer will kick off the github automation when the rest of the PR is populated)

Attribution

• AI coding assistants used: claude

[github-actions]

The PR description has been updated. Please fill out the template for your PR to be reviewed.

[planetf1]

NIT: Generic is imported but not used — MelleaTool picks up genericity via AbstractMelleaTool[P, R]. Project ignores F401 so CI won't complain, but it's dead code.

Suggested change

	from typing import Any, Literal, ParamSpec, TypeVar, overload

[planetf1]

NIT: MelleaTool[P, Any] with a module-level P collapses to MelleaTool[..., Any] under pyright and MelleaTool[Any, Any] under mypy — both type-check fine, but spelling it as MelleaTool[..., Any] is the explicit form for "unknown parameter spec" and matches what pyright shows. Worth updating the docstring Returns: line too.

Suggested change

	"""Create a MelleaTool from a LangChain tool object.
	def from_langchain(cls, tool: Any) -> "MelleaTool[..., Any]":

[planetf1]

NIT: Same as from_langchain — MelleaTool[..., Any] is the idiomatic spelling for "unknown parameter spec". Worth updating the docstring Returns: line too.

Suggested change

	"""Create a Tool from a HuggingFace smolagents tool object.
	def from_smolagents(cls, tool: Any) -> "MelleaTool[..., Any]":

[planetf1]

NIT: Both mellea/core/base.py (lines 958-959) and this module declare their own P = ParamSpec("P") / R = TypeVar("R"). Since MelleaTool subclasses AbstractMelleaTool, tools.py could import P, R from base.py for a single identity. Minor.

[planetf1]

I've left some minor nits, but otherwise LGTM

[akihikokuroda]

@planetf1 Thanks for review. I fixed them.