The more specific the question, the more useful the answer.

If the outreach is done by the HR then this could be an attempt by the employer to solicit feedback from job candidates, as part of an effort to improve the interview process.

A safe yet proactive strategy in this case is to appear open and helpful: "Overall I think it well well, giving me an opportunity to showcase my strengths while also learning more about the company and the potential fit. Are there any aspects in particular you are curious about?"

The last part is key. Yes, you are answering with a question, but this achieves two goals at once:

1. Gives them an opportunity to 'unpack' their question and make it more specific.
2. Buys you time to collect your thoughts and memories about the interview.

Even if that's all they wanted to know and have no further questions, they are walking away with an understanding that you had a positive and productive interview experience.

More importantly, such response communicates that you are open and willing to help while forcing them to be more constructive about the feedback they seek, rather than put you on the spot and sit back. It also makes an impression of you as a candidate who thinks before s/he talks. Good luck!

The more specific the question, the more useful the answer.

If the outreach is done by the HR then this could be an attempt by the employer to solicit feedback from job candidates, as part of an effort to improve the interview process.

A safe yet proactive strategy in this case is to appear open and helpful: "Overall I think it well well, giving me an opportunity to showcase my strengths while also learning more about the company and the potential fit. Are there any aspects in particular you are curious about?"

The last part is key. Yes, you are answering with a question, but this achieves two goals at once:

1. Gives them an opportunity to 'unpack' their question and make it more specific.
2. Buys you time to collect your thoughts and memories about the interview.

Even if that's all they wanted to know and have no further questions, they are walking away with an understanding that you had a positive and productive interview experience (assuming that it was).

More importantly, such response communicates that you are open and willing to help while forcing them to be more constructive about the feedback they seek, rather than put you on the spot and sit back.

Instead of a question-answer interaction, it creates a partnership space where both you and the solicitor are now collaborating around their goal of learning more about your interview experience. 

It also makes an impression of you as a candidate who thinks before s/he talks. Good luck!