“Too right!” Means “I Completely Agree”

“Too right!” means “I completely agree” or “exactly” in informal Australian English; it does not mean that something is excessively correct. It is stronger than a plain yes and often answers a judgement both speakers already feel they share.

“The rent has gone up again.” “Too right—and wages haven't kept up.” Here the second speaker is not measuring how right the statement is. They are endorsing it emphatically. With a lively tone, the phrase sounds warm and forthright. Said sharply during an argument, it can sound as though the matter is already settled. It is natural among friends; in a formal meeting, “I completely agree” followed by a reason is usually clearer. The expression is also used in British and New Zealand English, so it is not uniquely Australian.

https://dictionary.cambridge.org/dictionary/english/too-right
https://www.collinsdictionary.com/dictionary/english/too-right