The letter should identify the U.S. employer, state that the position is that of an agronomist, describe the professional duties in specific terms, give the expected duration and salary, and confirm the applicant's degree. It should be on letterhead and signed by someone with authority.
Write the letter for the officer who has never seen the job
The support letter is the single document most likely to decide a port-of-entry application, so it should be written for a reader who knows the USMCA profession list but nothing about the company. Open with the legal name and address of the U.S. entity and the applicant's full name and citizenship.
State the profession using the list's wording, then describe the duties concretely: sampling programs, fertility and seed recommendations, trial plots, grower training, reporting to a named agronomy manager. Give the start date, the requested period of up to three years, and the salary. Confirm that the company has reviewed Marguerite's bachelor's degree in agriculture and that the position requires it.
Avoid marketing language and avoid listing sales targets. Attach the parchment, the transcript, a résumé and proof of Canadian citizenship, and bring originals where possible, because photocopies of credentials sometimes prompt further questioning. Hypothetical example: Corinne, a Canadian soil-conservation specialist, receives a letter that calls her an agronomist but attaches only a sales brochure.
Her first review should produce a duty table matching each claimed task to a field report, trial protocol or reporting line. The transcript settles the credential point; the signed letter and job description settle the employment point. She should obtain the employer's current legal name and signatory authority before travel, because inconsistent entity names can make an otherwise sound package harder to assess.