What is the character limit for event description of a Google Calendar?

What is the maximum number of characters allowed in an Event Description (including spaces, punctuation, and URL

There is currrntly no documented limit for the length of the description in an event in google calendar.

I suspect that this would be due to the fact that google could change it.

I suggest you just try and save as much as you can in there and then handle any errors as they may come. TBH if memory services they just chop off what doesn't fit and dont respond with an error.