According to the Rehabilitation Act/ ADA the answer is: Yes, but… not necessarily with the exact accommodation that you are seeking.
If you are a federal employee who is disabled and you can show that you can perform the essential functions of your job with or without a reasonable accommodation and the agency cannot show that your request causes them an undue hardship then the agency must provide you with a reasonable accommodation! However (and this is a big however), the agency does not have to provide you with the exact accommodation that you are seeking. All the agency is required to provide you with is an effective accommodation or an accommodation that gets the job done!
In other words, lets say that an employee is suffering from anxiety or agoraphobia (fear of crowds), and requests to work at home full time in order to avoid large crowds of people. You can rest assured that the agency will likely argue that you are not entitled to work at home full time. Generally, the agency will argue that there are certain functions of your job that must be performed at the office, like meeting employees or meeting with your supervisor. If the agency offers the employee a quiet office away from people this arguably can be seen as an effective accommodation. Unless the employee can obtain a doctor’s diagnosis and letter stating that they can only work at home and any work in an office setting would be inadequate the employee may not be able to justify holding out for an accommodation of working at home. This would be a close call and would require medical documentation and opinion and a solid argument that the essential functions of the job could be performed at home.