Starting on 25 November 2020, /instrument/compositeIndex API will add sourcePrice, conversionIndex, conversionIndexPrice, and relation to the response body. This is to support the introduction of the Hybrid Composite Index.
Please refer to our blog for more details. This update is live now on Testnet.
This update is part of our continuous improvements to the BitMEX Index. If you have any further questions, please contact Support.