refactor: create_tool_from_function + tool decorator

[anakin87]

Related Issues

Since we are introducing some subclasses of Tool (ComponentTool, OpenAPITool in the future, ...), the Tool.from_function class method becomes inappropriate. These subclasses would inherit the method, potentially leading to unintended behaviors (e.g. ComponentTool.from_function makes no sense).

To address this, I'm proposing a replacement: create_tool_from_function utility function (+ a tool decorator).

Proposed Changes:

• Replace the Tool.from_function class method with a create_tool_from_function utility function.
• Add a simple tool decorator, to simplify programmatic use cases

Examples

from typing import Annotated, Literal
from haystack.tools import create_tool_from_function

def get_weather(
    city: Annotated[str, "the city for which to get the weather"] = "Munich",
    unit: Annotated[Literal["Celsius", "Fahrenheit"], "the unit for the temperature"] = "Celsius"):
    '''A simple function to get the current weather for a location.'''
    return f"Weather report for {city}: 20 {unit}, sunny"

tool = create_tool_from_function(get_weather)

print(tool)
>>> Tool(name='get_weather', description='A simple function to get the current weather for a location.',
>>> parameters={
>>> 'type': 'object',
>>> 'properties': {...},
>>> function=<function get_weather at 0x7f7b3a8a9b80>)

from typing import Annotated, Literal
from haystack.tools import tool
@tool
def get_weather(
    city: Annotated[str, "the city for which to get the weather"] = "Munich",
    unit: Annotated[Literal["Celsius", "Fahrenheit"], "the unit for the temperature"] = "Celsius"):
    '''A simple function to get the current weather for a location.'''
    return f"Weather report for {city}: 20 {unit}, sunny"

print(get_weather)
>>> Tool(name='get_weather', description='A simple function to get the current weather for a location.',
>>> parameters={
>>> 'type': 'object',
>>> 'properties': {...},
>>> function=<function get_weather at 0x7f7b3a8a9b80>)

How did you test it?

CI, new tests

Notes for the reviewer

I also reorganized the code by moving functionalities into separate modules.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 12695370849

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 91.099%

---

Totals
Change from base Build 12694180152:	0.005%
Covered Lines:	8659
Relevant Lines:	9505

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 12695378991

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 91.099%

---

Totals
Change from base Build 12694180152:	0.005%
Covered Lines:	8659
Relevant Lines:	9505

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 12695708412

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 91.099%

---

Totals
Change from base Build 12694180152:	0.005%
Covered Lines:	8659
Relevant Lines:	9505

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 12707767349

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 91.099%

---

Totals
Change from base Build 12694180152:	0.005%
Covered Lines:	8659
Relevant Lines:	9505

---

💛 - Coveralls

[vblagoje]

Left a small comment but more importantly I think we need to clarify and document what parameter inputs types are supported for the function passed to create_tool_from_function and tool decorator.

[julian-risch]

Looks good to me! 👍 @tool decorator is an interesting idea!