but then nothing wil notice if you say {-# TOOL HLNIT ... #-} by mistak
This seems fixable. Any tool can slurp in all `TOOL` (or `X-`, which I prefer) pragmas and look for ones that appear to be misspellings. Of course, this doesn't stop me from writing a tool named HLNIT and using those pragmas, but we'll never be able to guard against that.