Originally Posted by AerocatS2A
It is certainly a requirement to contact ATS 2 minutes prior to TOD (or any other level change) so they can pass traffic. The best way I've heard this carried out is,
"ABC 2 minutes top of descent"
"ABC, traffic is bla bla bla"
<<2 minutes later>>
"Centre and all stations Broome area, ABC 30 miles SW of Broome, leaving FL130 on descent, Broome at 32"
You get your traffic in good time, you then make the leaving call as well as alerting any VFR traffic in the area of where you are and what you are doing.