@aymeric-roucher and @albertvillanova, what do you think about this solution?

I think the problem before was that getting the func, in this case the forward method, from cls.__dict__.items(), doesn't preserve the __source__ field which is set in tools.py#L977. From my testing, using getattr works better in this regard as it preserves the __source__ field. When the __source__ field is preserved it is used by get_source to successfully transform the function into code.

So with the fix the resulting tool source for my example becomes:

class SimpleTool(Tool):
    name = "magic_number_tool"
    description = "This tool returns the magic number."
    inputs = {}
    output_type = "integer"

    def __init__(self):
        self.is_initialized = True

    def forward(self) -> int:
        """
        This tool returns the magic number.
        """
        return 12345

Instead of:

class SimpleTool(Tool):
    name = "magic_number_tool"
    description = "This tool returns the magic number."
    inputs = {}
    output_type = "integer"

    def __init__(self):
        self.is_initialized = True

    @tool
    def magic_number_tool() -> int:
        """
        This tool returns the magic number.
        """
        return 12345

Thanks for the proposed solution, @tobiasofsn.

I think the error is caused by other part of the code. See comment: #1345 (comment)

Please, feel free to reopen if you think otherwise.

Hi @tobiasofsn.
After investigating further, I think the issue is caused by the line you proposed to fix. Thanks!
That said, I'd approach the fix a bit differently, so I've reopened your PR and will push a commit with the updated solution.