To centrally manage all of your LE certificates, keys, alerting, etc. You can also more easily use LE certs in a wider array of scenarios too. Check out the docs to learn more.
I did have a look at the docs, but they more explained the how, rather than the why - I missed some kind of intro/overview explaining the value proposition.
I'm still a bit fuzzy on this - why would I want alerting, for example? Automation is a big part of LE, and my certs are configured to auto-renew. If that was to fail for some reason, then LE will send me an email - is it this part where this tool comes in, providing improved alerts where automation has failed?
That's great feedback. I'll update the docs to better explain the why.
To elaborate on the why for alerting, there are many situations that I've seen where things change and subsequently fail silently. Perhaps some dependencies, or maybe configuration changes, caused things to break. Also, alerting doesn't only have to be for your certificates. You can point to any endpoint to monitor as well. There are three aspects of alerting: changes to the cert (perhaps you care about a 3rd party certificate and its underlying key changing), failure to renew, and expirations. Each comes with its own benefits and use cases.
To expand on the why a bit further for the project as a whole, it's really as a way to help consolidate and centralize things. I've seen many disparate ways of using Let's Encrypt. From various clients to some hacks to better support more complicated scenarios. By separating obtaining the certificate from applying, it helps facilitate many things, like using LE certs behind load balancers & proxies, non-standard ports, things that don't speak HTTP, etc.
If certificate expiration continues to decrease in time, we'll need some capabilities to exchange certificates in an automated fashion as well. I'd also like to incorporate Certificate Transparency logs so you can be sure no one has issued certs for your domain(s). There are many cool and interesting scenarios but mostly the challenges come when managing things at scale. So, it's not really all that useful if you're only managing one or two certs.
