Where are the HTTP/service docs for distributed tracing (performance monitornig)?

I’m trying to write an updated version of Haskell SDK and am unable to locate how to send “traces, transactions, and spans” to Sentry (as documented at https://docs.sentry.io/product/performance/distributed-tracing/#traces-transactions-and-spans). I’m referring to the SDK development docs at https://develop.sentry.dev/sdk/

I think I found something at Home > SDK Development > Unified API > Guidelines for Tracing Support - Please let me know if this is not the correct page (or if there are better docs available elsewhere).

PS: Strangely, I am unable to post the direct link.