but he had a bad night at work so the timing didn't feel right. But not telling him right away made me feel like I was hiding something even though I was just waiting for the right moment.
This is an important part of the answer to your question - I think. When in doubt, we do our best
It's not always easy to say things straight away. If you don't have clear rules around this, then - as you did - you make the best call you can (and sometimes get it wrong).
I feel very grateful that my partners trust me to say things on a 'need to know' basis. We have a culture of sharing (but not over-sharing) but we also don't have many specific requirements as each situation has its unique aspects!
Clearly one concern here is whether you are "hiding" or "being secretive"... well, are you? In this case, sounds like you weren't. Does your husband trust
that you have good intentions, and do not buy into hiding/secrecy? Then, if anything SEEMS like it is 'secretive', he can also KNOW that it is not. And you can go forward together on that basis.
I would consider that level of trust minimal for me to roll a healthy non-monogamy with anyone.
As for whether you should have rules/not, that's obviously nothing anyone else can say. It will be whatever works for youru and your partners. Whatever you need to navigate this stuff