what does lulu doctor do?
Answers "why is it not working" in one screen: every place that was looked at, what was wrong with the key as a string, whether the endpoint is reachable at all, and what the one test call cost.
how do you run it?
In the parser’s own words, find the key, test it, and price the call. Every flag this build accepts, on one line:
lulu doctor [--provider PROVIDER] [--offline]
lulu doctor ± find the key, test it, price the calllulu doctor --offline ± everything except the call, so nothing is spent
what does it print?
Every place it looked, in order, whether or not it found anything. One screen that says why it does not work, or proves that it does.
Where the code cannot know something it says so. A rejected key names the states that produce that rejection rather than printing a status code, and an unknown price is "no published price on file", not a plausible number.
is a missing key an error?
No. Without a key lulu doctor --offline exits 1, which is the answer and not a fault: it is telling a new reader the one thing that is missing. What would be a fault is a traceback, and every push to this repository installs the package into an empty environment and runs this exact command to make sure there is not one.