Hi Youness – The UUID in the extension.toml is not the functionId, it’s a new app-relative identifier that solves the extension-matching issues you may have seen in the past when deploying. You still need to use the shopifyFunctions query to get the global UUID for the functionId parameter.
We know this is confusing 
… and have some ideas on how to fix this experience. Meanwhile, let us know if the ID in shopifyFunctions works.
-Nick