What it covers
==============

Your reading is correct. All of these examples fall under the Use an Object action. The wording is very clear:

> **Use an Object (PHB p. 193)**

> When an object requires your action for its use, you take the Use an Object action. 

As Eric pointed out in a comment, the Thief Archetype for the Rogue gets to Use an Object as a bonus action. They would be able to poison, drink potions, or spread caltrops as a bonus action.

What it does not cover
======================

Activating a magic item does not use the Use an Object action.

> **Activating an Item (DMG p. 141)**

> If an item requires an action to activate, that action isn't a function of the Use an Item action, so a feature such as the rogue's Fast Hands can't be used to activate the item.