Their evidence should be consistent about the actual arrangement, although each may explain the part it knows. Identical wording is not a substitute for accurate responsibilities.
Use complementary evidence
Identify who employs the applicant, who receives the services and who assigns each major activity. Project specifications can explain the work without becoming a substitute for the professional offer and qualifications. Resolve real discrepancies; do not obtain matching signatures on a description the parties will not follow.
Carry proof of citizenship, the current employer support letter describing qualifying professional duties, credential documents, the most recent I-94 and admission record, and the receipt notice for whatever is pending. Build the record around the whole engagement: the employer letter or contract, start and end dates, weekly schedule, work location, compensation, professional deliverables, and duties during both peak and quiet periods. TN admission is tied to the employment described, so a professional taking two part-time American positions needs a letter from each describing professional duties within the listed occupation, and an employer added after admission requires a fresh application rather than an explanation at the counter.