I'm not a fan of the invocation in the example. It's doing a pip install AND running the script in whatever env is active (if any), which can easily lead to problems. This is unacceptable today with the existence of uv. Either advocate uv script functionality, or explicitly document that the user should create an env and ensure it's active when running Claude Code.
The deny-with-reason is undersold here. Most hook frameworks treat denials as the end of the road: the LLM hits a wall, retries blindly, and gets blocked again.
Feeding the reason back into Claude's context could break that cycle much faster.
One question for the author: when several hooks fire, does Claude get all the denial reasons concatenated, or does the first deny win?