Sloeber expects the tools folder to be in a different folder about arduino_tools

[fpistm]

I guess you use the git repo and not the package one?
The platform.txt in the repo is not exactly the same than the one packaged.
In the git repo:
{runtime.hardware.path}
is replace by:
{runtime.tools.STM32Tools.path}

This is mentioned here:
https://github.com/stm32duino/wiki/wiki/Using-git-repository#31-cloning-the-git-repository-to-replace-the-stm32-core-version-package-1st-method

[swissbyte]

Interesting.

I have added the package json path in sloeber and let them download all files by them self.

[fpistm]

So, you should not get this issue if you use only the package.
Did you check the platform.txt ?
You should have:
tools.serial_upload.path={runtime.tools.STM32Tools.path}/tools/win

[swissbyte]

ok i got the problem.
I have messed up something during developing code for the generic STM32F0.
It was a problem with the git repo. as you already told me.

Sorry for the inconvenience.