The MSCA explained by your National Contact Points
It is a contractual obligation to establish a Career Development Plan between the researcher and supervisor. Does the Commission/REA check the CDP at any point?
The REA does not check the Career Development Plan nor request a copy of it. This is a work document agreed between the fellow and his/her supervisor at the beginning of the fellowship (though it can evolve over time) and it is kept internally at the beneficiary's level.