It should identify the profession, describe the duties the person will perform, state the credential relied on, and place the training as orientation to the employer rather than as qualification for the role. A separate training schedule supports that description. Ask also that the schedule be dated and issued by whoever owns that record, since an undated draft forwarded by a recruiter is hard to rely on and easy to contradict later. A version number on the document helps more than another paragraph of description.
Reconcile the letter with everything else in writing
Recruiter emails, an internal onboarding plan and the formal letter often describe the first weeks differently, and the applicant is the one who has to explain any gap. Read them side by side and ask the employer to correct whichever is inaccurate, before the package is assembled. A letter that contradicts a schedule attached to it is weaker than either document alone.
Hypothetical example: an interior designer accepts a position with a millwork specification group whose letter promises eight weeks of shop-standards training, while the attached onboarding schedule shows no specification packages produced until week nine. Reading the two together, she asks the employer to reissue the schedule identifying which packages she will author from the first week. If that cannot honestly be said, the sensible response is to reconsider the role rather than to keep redrafting the paperwork around it.