mentally sharp or clever
astute - clever
An ‘astute’ person has the ability to accurately assess and understand people or situations. This skill often helps them to side-step problems and also turn them to their advantage, though typically not at the expense of others. For that reason, this term has positive connotations.
That’s a very astute observation you have made. You clearly have an excellent eye for detail.
At first I wasn’t sure about the person the committee selected for the role, but it soon became clear that they had chosen astutely.
With characteristic astuteness, Helen foresaw the financial crisis and put safeguards in place to protect the business.