In the Army they have a particular form. However, what I did; I executed my own assessment in writing. I then sat down with the Commander and asked if he agreed. I focused on how the medical issues affected my performance in my duty position. I listed all my medications and every medical issue that affects my daily day. Specifically; address how it affects you on a daily basis ie missed time from work and lack of performance. I would also get others to attest to this (peers/supervisors). The end result; explained how I was in the past ( doer and performer) and now based on situation. Spell out at exactly how it impacts you; deployablity is not really an issue but can be included. Key note; an annual evaluation is just that but doesn't really portray your inabilities.
I am no expert but my thought is the more concrete evidence that points in the direction you want will help.