Penmentor Lets Students Get AI Feedback on Handwritten Math Work

How Real-Time AI Marking Works

A new tool called Penmentor uses artificial intelligence to review handwritten mathematics assignments in real time. Students write by hand in the Xournal++ app, press a single key, and receive feedback from AI models Claude, Gemini, or GPT directly on their digital page. The system marks work with colored annotations, offers hints rather than full solutions, and generates animated explanations similar to 3 Blue1 Brown videos.

Created by developer Abdullah Alhariri, Penmentor aims to replicate the experience of working alongside a human tutor. Instead of simply grading answers, the AI highlights mistakes, circles problematic integrals, and guides students toward discovering solutions independently. The feedback appears instantly on the student’s screen, mimicking the feel of a teacher leaning over their shoulder with a red pen.

Penmentor connects the Xournal++ handwriting application with major AI models through a simple keyboard shortcut. When a student finishes a problem, pressing the assigned key sends their handwritten work to the chosen AI service. The model analyzes the solution, identifies errors, and returns annotations that appear directly on the page. These comments use different colors to distinguish between conceptual misunderstandings, calculation errors, and formatting issues.

Can AI Replace Traditional Math Tutoring?

The system also generates visual explanations for complex topics. After marking an integral, for example, Penmentor can produce a short animation showing how the area under a curve is calculated. This feature draws inspiration from popular educational content creators who use dynamic visuals to explain abstract mathematical concepts.

While Penmentor doesn’t fully replace human instruction, it provides immediate support that many students lack outside classroom hours. Traditional tutoring often requires scheduling and can be expensive, whereas this tool offers round-the-clock assistance. However, educators note that AI feedback works best when combined with human guidance, particularly for deeper conceptual understanding.

The project has gained attention on Hacker News, where developers and educators discussed its potential and limitations. Some users praised the intuitive interface and helpful hint system, while others questioned whether AI models consistently interpret handwritten symbols accurately.

Looking ahead, Alhariri plans to expand Penmentor’s capabilities. Future updates may include support for additional subjects beyond mathematics, integration with other note-taking applications, and improved recognition of diverse handwriting styles. The goal remains clear: making personalized academic support accessible to every student.

Frequently Asked Questions

What applications does Penmentor work with? Penmentor currently integrates with Xournal++, a popular open-source note-taking app used by students for handwritten notes and problem-solving.

Which AI models can mark my work? Users can choose between Anthropic’s Claude, Google’s Gemini, and OpenAI’s GPT models to review their handwritten solutions.

Is Penmentor free to use? The tool itself is open source, but users must provide their own API keys for the AI services they want to use, which may involve usage costs.