An important function of successful communication as a leader is giving someone performance-related feedback. Many professionals resist giving feedback to avoid tension or conflict. Even when feedback is provided, the delivery might unintentionally damage relationships. Fortunately, feedback can be effective and positive.
The basics of delivering great feedback are pretty simple. Be very specific, not general or vague. Never tell someone they can do better without specifying or quantifying exactly how.
Be concrete. Phrases like "I know you can be a better developer" mean nothing compared to "I want you to shoot for 100% code coverage for all customer-facing APIs." The second statement is more specific and measurable.
Good feedback is always delivered positively. Even difficult feedback can be delivered in a positive light. How the comments are framed determines this. For example, a negative frame may be telling someone their brute force search approach is too slow. A more positive frame would be telling them their algorithm could be 100x faster if they used a tree index. The positive frame is more useful.
You should also consider the amount of feedback you give. Everyone has a different ability to digest feedback meaningfully. Only give feedback you honestly feel they can take. If you give too little, it does not provide enough direction. Too much feedback may offend them. Strive to provide what teammates need without exceeding what they can take.
An often overlooked part of great feedback is ownership. This involves using "I" statements. For example, "I rated you a 3 because..." then explain. This way you never blame an issue on someone else - or the rating system. With this approach, the feeling of defeat is minimized and the opportunity to improve is clear. You own the situation and take responsibility.
Great communication is not complicated. Be proactive, use the right channels, respect and use feedback correctly, and listen more than you talk. That is strong communication.