Born in Drogheda, O’Toole grew up in Australia, where he played for the Queensland Schoolboys before swapping life down under for Ulster and enrolling at Campbell College. The then 19-year-old joined the Ulster Rugby Academy in 2017, and having delivered a series of outstanding performances for Ulster A in the then British & Irish Cup, he was rewarded with his senior debut in April 2018 against Edinburgh. The former Irish U20 international followed up an impressive end to the 2017-18 season by going on to make a further 18 senior appearances in the following year, earning himself a senior contract in the summer of 2019. O’Toole received his first international call-up to the 2020 Irish Six Nations squad, and made his debut for Ireland against USA in July 2021. O'Toole was called up to Ireland Head Coach Andy Farrell's 2023 Six Nations squad.