[BUG] Tool defined in class triggers TypeHintParsingException

[faev999]

Describe the bug
Defining class instance methods as a tool raises:
smolagents._function_type_hints_utils.TypeHintParsingException: Argument self is missing a type hint in function test_tool

Code to reproduce the error
example:

from smolagents import tool, CodeAgent, LiteLLMModel
import os


class Test:
    @tool
    def test_tool(self, text: str) -> str:
        """
        A test tool that takes a text as input and returns a string.

        Args:
            self: The class object.
            text: The input text.

        Returns:
            stringer the output string.
        """
        stringer = f"This is a test tool. The text is: {text}"
        return stringer


model_manager_agent = LiteLLMModel(
    model_id="cerebras/llama-3.3-70b",
    api_key=os.getenv("CEREBRAS_API_KEY"),
)

manager_agent = CodeAgent(
    tools=[],
    model=model_manager_agent,
    # prompt_templates=pepper_prompt_templates,
)
test = Test()

manager_agent.tools["test_tool"] = test.test_tool


manager_agent.run("what's up?")

Error logs (if any)

smolagents\_function_type_hints_utils.py", line 287, in _convert_type_hints_to_json_schema
    raise TypeHintParsingException(f"Argument {param.name} is missing a type hint in function {func.__name__}")
smolagents._function_type_hints_utils.TypeHintParsingException: Argument self is missing a type hint in function test_tool

Expected behavior
I am trying to define tools inside classes, so I have access to other methods and properties

Packages version:
1.9.2

Additional context

This happens with both ToolCalling and Code agents.

I briefly looked inside the docs to see if this case is already covered, but could find anything related except the e2b_example, which is not so close to what I want.

If I modified my example like this def test_tool(self: Any .... then I get:

smolagents\tools.py", line 878, in tool
    new_signature = original_signature.replace(parameters=new_parameters)
Lib\inspect.py", line 3068, in __init__
    raise ValueError(msg)
ValueError: duplicate parameter name: 'self'

That happens because line new_parameters = [inspect.Parameter("self", inspect.Parameter.POSITIONAL_ONLY)] + list( original_signature.parameters.values() )

Is already prepending a "self" parameter (declared as positional only) to the list of parameters from the original function signature.

[faev999]

Is there a reason prepending that 'self' in that line new_parameters = [inspect.Parameter("self", inspect.Parameter.POSITIONAL_ONLY)] + list( original_signature.parameters.values() )

I removed that part and ran the test suite (plus my own code) without Failures pointing to that modification

[sysradium]

Have you tried this PR #627?

[faev999]

No, but it seems that's what I am looking for, I will give it a try. Thanks for the info