◇ Could this help me?
Yes. Reviewing a third-party skill or connector before installing it is exactly the right instinct, the threat described is real, and doing the review in a session that has no access to your keys or filesystem is the correct shape for it. Do not treat the resulting good or bad verdict as a guarantee: a model review catches obvious malice and misses subtle or obfuscated behavior, so pair it with checking the publisher, the update history, and the permissions actually requested. This is a general practice.
I am considering installing a third-party skill or connector server. Before anything is installed, review its contents and report: what the code actually does, every file and environment variable it reads, every network destination it contacts and what it sends there, every command it can execute, and any obfuscated or dynamically loaded code. Then tell me who publishes and maintains it, how actively it is maintained, and what permissions it requires. Give me a recommendation with your reasoning and the specific lines that drove it. Do not install anything.