Judicial officer Sharif McKee had originally called for a 10-match ban over O'Toole's challenge on Nankivell, which resulted in the Munster center sustaining a hamstring injury.
In a statement posted on their website, URC explained that O'Toole was given a 40% mitigation due to his “admission of error and immediate apology and again after the match”.
However, given O'Toole had previously received a red card for 'foul play' against Toulouse in 2022, 'not all mitigating factors applied'.
Interim coach Simon Easterby said in a URC statement that O'Toole would have “barring injury or suspension, a very good chance of being selected in the matchday squad” as he had been “a permanent member of the Irish senior squad ever since”. Debuting in 2021.”
As a result, the URC felt it was “appropriate” to include Ireland’s formulations in the ban.
After the England and Scotland matches, Ireland, aiming to win a third successive Six Nations title, face Wales away and France at home before finishing the season against Italy in Rome.
Easterby, who takes caretaker charge of Ireland while Andy Farrell prepares to lead the British and Irish Lions on their tour of Australia in the summer, will name the Six Nations squad on Wednesday 15 January.