Before you run a deploy for the first time, it's a good idea to check that everything is set up correctly. That's what scotty doctor does:
scotty doctor
It runs through a series of checks:
- Scotty file exists and can be found
- File parses successfully without syntax errors, and shows how many tasks and macros were found
- Servers are defined in the file
- Tasks are defined in the file
- Macros reference valid tasks so you don't get surprised mid-deploy by a typo
- SSH connectivity to each remote server, including connection timing
- Remote tools checks whether
php, composer, node, npm, and git are available on each reachable server

This is especially useful after setting up a new server, when debugging connection issues, or before your first deploy to a new environment. If something is off, doctor will tell you exactly what.