What items are announced to chat when bought?

I have noticed that some items get announced to chat when purchased, what items gets anounced and what makes them so special?

Solution 1:

Items that provide "team support".

• Wards
• Oracle's Extract/Elixir
• Items that grant an aura to allies or a debuff to nearby enemies

This is so that (1) people know that you are spending money for the team and (2) so that your allies don't double up on an aura item accidentally.

Solution 2:

Support items that help your team or debuff the enemy team. These include (off the top of my head):

1. Sight Wards/vision wards
2. Oracle's Elixir
3. Aegis of the Legion
4. Frozen Heart
5. Shurelya's Reverie
6. Locket of the Iron Solari
7. Zeke's Herald
8. Will of the Ancients

Solution 3:

From the official patch notes:

Important items purchased by your team will now be called out in chat (Aura items, Sight and Vision Wards, top tier items, etc)

Wards, Aura Items, and Legendary items all show up in chat.