“Good Call” Means “That Was a Sensible Decision”

In everyday Australian conversation, Good call. commonly approves a particular decision or suggestion. It means ‘that was a sensible judgement’, not ‘that was a good telephone call’.

A: Let’s take the earlier train. There’s track work later.
B: Good call.

Good idea can also approve a suggestion, but good call focuses more closely on someone choosing well in the circumstances. The expression is brief and informal, and is normally sincere; an exaggerated tone can make it sarcastic. It is not uniquely Australian and sounds natural in Britain and the United States as well. In formal writing, use ‘That was a sensible decision.’

https://dictionary.cambridge.org/dictionary/english/good-call