When requesting letters of recommendation for a PhD application in theoretical physics, it's important to understand that you cannot dictate the content of these letters. However, providing your recommenders with relevant information can enhance the quality of the letters. Many universities offer general guidelines for recommendations, but these may lack specificity. It's crucial to choose referees who can provide detailed insights into your abilities and experiences. If you have concerns based on past experiences with minimal letters, consider offering to share your academic record or specific strengths you would like highlighted, but do so delicately to avoid overstepping. Communication with your referees about what to include can be beneficial, especially if they are less experienced in writing such letters. Ultimately, the goal is to ensure that the recommendations reflect an independent and informed perspective on your qualifications for doctoral studies.