Additional Overlay that doesn't overlap with Autocomplete

I am adding support for an obscure language and I am trying to add an additional overlay decoration that provides additional information about the function you are calling. Specifically, it shows the function definition with the current parameter in bold. I want it to behave similar to how it works in Visual Studio like in this example.

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Problem is when I create an overlay decoration it overlaps with the autocomplete overlay. Any recomendations on getting this to work?