A karana is half a tithi — six degrees of the Moon's separation from the Sun, roughly eleven to thirteen hours. There are eleven names: seven movable ones that each repeat eight times through a lunar month, and four fixed ones that occur once each. Vishti, usually called Bhadra, is the one that is avoided.
This endpoint finds every occurrence of one named karana across a whole calendar year, so you can build a 'when is the next Vishti' list without walking the year day by day. Pass karana_name exactly as spelt in the field's list (it is case-sensitive), year, and timezone_as_float; the offset defines where the local year begins and ends. No latitude or longitude is needed, because a karana is a purely lunar quantity.
The response is {year, karana_name, rows}, where rows is a chronological list of {start, end} timestamps in UTC. A fixed karana yields about twelve rows a year and a movable one closer to a hundred. For the karanas of a single day, use the karana_segments key on /api/astro/panchanga/ instead.
UTC offset of the place, in hours, as a decimal. Example: 5.5 for India (UTC+05:30), -5 for New York in winter, 5.75 for Nepal. This is NOT validated against date_time - if the two disagree you get a successful response for the wrong moment, so derive both from the same source. Use the offset in force on that date, not today's: a summer birth in a country with daylight saving needs the summer offset.
year
integer
required
Year of birth as a number, e.g. 1990. Four digits.