When adding a person with just his name, the error message is still invalid command format and does not actually show that it is because adding phone is compulsory. May be you can make a specific message dealing with this or make current error message more clear like clarifying what information is compulsory and what is optional (just like what you did in the UG), otherwise it may confuse the users a lot as he may think he needs to add all the information based on the error message, which is inconsistent with the UG.
When adding a person with just his name, the error message is still invalid command format and does not actually show that it is because adding phone is compulsory. May be you can make a specific message dealing with this or make current error message more clear like clarifying what information is compulsory and what is optional (just like what you did in the UG), otherwise it may confuse the users a lot as he may think he needs to add all the information based on the error message, which is inconsistent with the UG.