Is 'kind lying' part of the social agreement?

Depends on the person and situation, but yes. We have so many expectations which are different from what we literally communicate like this, speed limits, saying "this was great, I'll call you some time", "wow that was the best X ever", "no problem", "sorry boss, I had food poisoning", etc.

We all lie constantly whether by commission or omission, sometimes the lies are just a societal convention. We often have a default level of deception and then tailor our honesty and bluntness as we get to know the person more (sometimes opting for less truthfulness)

I find this fascinating and difficult at the same time. I thought I read somewhere recently that The Four Agreements was recommended to read. The first Agreement that can help shift your life in a new direction is Be Impeccable With Your Word.

This coupled with a practice of Ruthless Compassion, can lead to some very blunt and deep answers for a question.

Neither of those approaches include judgement as part of the delivery. Though I can say in past relationships, and before doing a ton of work on myself, it was easier to omit details or lie to someone than own my actions or placement.

My standard I am seeking to live by is to answer as truthfully and compassionately as possible what is being asked of me. I think it would almost always require getting more information before answering. Like 'For what occasion?', otherwise there is not enough info.

It may be the coach in me, or the men's team work, or the impatience at times, but I do my best to be direct once I have enough information to answer from my experience.