Documentation for built-in types only works once

[brettcannon]

If you launch VS Code and then type str(), you will get the documentation for the str type.

But if you type str() again on another line, like so:

str()
str()

you will get a message saying that "Documentation is still being calculated, please try again soon."

[CodySchrank]

Also happening to me with custom types

[MikhailArkhipov]

microsoft/PTVS#4623