Verifying tools are active / inactive

I am also looking for code to tell if particular tools are inactive.
I want my sequence to validate that all the required tools are available before attempting to proceed.

The sequence I am building required three tool changes and a seed bin. When it ran, the code failed poorly when it could not find the seed bin. The sequence to stopped. I want to make it resilient with informative warnings instead of this.

Which is unhelpful. What I want to do is perform a prerequisite check to see if the sequence can be run.