From Resume to Cover Letter With AI, Without New Facts

The easiest way for an AI cover letter to go wrong is also the most tempting: it tries to bridge the gap between what a job asks for and what your resume proves. A tool from the posting becomes a tool you used; a result you never measured becomes a confident percentage; a generic greeting turns into a name nobody supplied.

Johnson & Johnson makes the risk plain in guidance for applicants: a vague prompt can be read as a license to invent, and factual inaccuracies in application materials are not tolerated. Starting with your resume gives a draft better material, but it does not remove the need to check it. The safe rule is simple: the posting tells the letter what to emphasize; your resume and your own notes decide what it may claim.

Keep facts and directions separate

Harvard’s Mignone Center for Career Success has two pieces of advice for tailoring a letter. One is “Reference skills or experiences from the job description and draw connections to your credentials.” The other is “Give examples that support your skills and qualifications.” Both run in one direction. The job description tells you which of your credentials to bring forward; it does not add to them.

That splits what a letter tool receives into two kinds of input. Facts about you come from your resume and from anything you type about what to stress. Directions come from the job posting, the company and role you name, and the tone and length you choose. A good draft uses the directions to choose among the facts and uses nothing else as a fact.

The rest of this guide quotes the letter writer in the resume builder we sell, so weigh what we say about it with that in mind; each account of how it behaves is based on its code. The instructions it gives the model draw the same line almost word for word: the job posting “is not a fact about the person,” and it may be used only to pick which facts to stress and how to open. For a skill the job asks for and the resume does not show, the instruction is “Do not mention such a skill at all, not even to say the person is learning it.”

Harvard is also blunt about AI itself: “Generative AI should not be the primary author—not least because its output will likely be very generic.” A tool that writes the whole letter is, by that standard, producing a first draft, and the rest of this guide treats it as one.

Use a blank when you do not have the number

A draft that wants to show a result needs a figure for it. If your resume has the figure, the letter can repeat it. If it does not, the honest output is a blank. Our letter writer’s instructions ask for a short placeholder in square brackets where a measurable result would help and none was given, at most four in a letter, and they add: “A placeholder holds a label only, never a guessed value.”

Code backs those instructions up: after the model has answered and before the letter reaches the editor, the server goes through the reply one sentence at a time. Any number missing from your resume, your notes, the company name and the role becomes “[X]”, and a dollar or percent sign beside it stays where it was. That includes a number copied from the job posting, since the posting is not your text. A count of years gets through if it fits within the stretch between the first and last years on your resume, which caps the figure without proving the years were spent the way the sentence says. A sentence that would push the letter past four blanks is taken out instead of being added with a fifth. The post on AI bullet points and their numbers follows a check of the same kind through a single bullet.

Names get the same treatment, with one difference: a sentence that fails is removed, not patched. The check looks for a capitalized word in the middle of a sentence, or a word shaped like a product name (mixed case, digits inside a word, a plus or a hash sign), that none of your own text contains. A name the job posting has, such as the employer’s own product or team, may stay. A name the posting lists among the job’s skills or tools may not, because it describes the job and not you.

A letter that sounds good but claims too much

Everything in this example is invented: the person, both employers and the posting. Maya Torres is an office coordinator, and her resume holds one job:

Office Coordinator, Brightwater Property Group, Mar 2021 - Present

Scheduled maintenance visits for 140 rental units across 6 buildings. Moved the vendor invoice log from paper to a shared Google Sheets file. Answered tenant calls and emails, about 30 a day.

Skills: Google Sheets, QuickBooks, scheduling

She is applying for an Operations Coordinator role at Harbor Lane Clinics, and the saved posting lists Salesforce, Excel and vendor management as skills. We wrote the draft below ourselves and put the faults in on purpose; no tool produced it, ours included.

Dear Ms. Ortiz,

I’m applying for the Operations Coordinator role at Harbor Lane Clinics because I keep maintenance running for 140 rental units across 6 buildings.

At Brightwater Property Group, I schedule maintenance visits for those units and cut vendor wait times by 25%. I moved the vendor invoice log from paper to a shared Google Sheets file, which saved the team 10 hours a week. I also built weekly reports in Salesforce for the leasing team.

I answer about 30 tenant calls and emails a day, and I bring 5 years of experience in operations. My manager, Linda Park, relies on me for vendor calls.

I’d welcome a conversation about how I would organize vendor scheduling across your clinics in my first months.

Sincerely, Maya Torres

We handed the draft, exactly as printed here, to the server function that screens each letter the model returns. That was on October 31, 2026. Two of its seven sentences were removed: the Salesforce one, because the posting asks for Salesforce and her resume never mentions it, and the one naming Linda Park, a person none of the inputs mention. The 25% became “[X]%” and the 10 hours became “[X] hours”, because she never wrote either figure. Her 140 units, 6 buildings and 30 calls a day stayed, since they are hers. The greeting came back as “Dear Hiring Manager,” and the sign-off as “Sincerely,” without the name. The letter survived with four paragraphs and two blanks.

When we added her notes on what to stress, “Vendor wait times dropped 25% after I set up the shared calendar,” the 25% stayed in the letter, because it was now her own figure. When we changed the last paragraph to promise she would “use Excel to organize vendor scheduling,” the result was different, and the next section explains why.

When the draft should be thrown out

With the Excel sentence removed as well, three of the seven sentences had failed, and the guard returned no letter at all. Its rule is that a draft which lost more than 40% of its sentences “is no longer the letter the model wrote,” so it is discarded rather than handed over with holes. A draft that keeps fewer than two paragraphs after the checks is discarded the same way.

For the person writing, that shows up as an error asking you to try again, and the request is handed back to your daily allowance (the server caps how many refunds one account gets in a day). The request is also refused before any writing starts when the resume has almost nothing in it besides a name, because then every fact in the letter would have to be made up.

Names need the same care as numbers

Harvard’s guide says “Address your letters to a specific person if you can.” Our letter writer keeps a name in the greeting only when the saved job posting contains it; otherwise the greeting is “Dear Hiring Manager,” in the letter’s language. That rule is stricter than it looks. In our run, “Dear Ms. Ortiz,” fell back to “Dear Hiring Manager,” even after we added her full name to the posting, because “Ms” itself is not in it, while “Dear Dana Ortiz,” was kept. If you know who will read the letter, type the greeting yourself in the editor.

The sign-off never carries a name. The name printed under it is taken from the resume the letter was written from, in a field you can edit, and that resume’s contact details head the page.

Treat a blank as work left to do

Fewer blanks come back if your figures are already in the request. The letter form has a field for what to stress, up to 600 characters in your own words, and a figure written there counts as yours, as the 25% did in the example. Tone (Professional, Warm or Direct) and length (Short at about 150 to 200 words, Standard at about 250 to 350) are set in the same form.

Whatever blanks remain are marked on the page and listed above it with a count. Replace each one with a number you can explain, or delete the sentence. The editor does not stop you from downloading the PDF or Word file with a blank still in it, so a “[X]” you overlook goes out with the application. Every line is editable, paragraphs can be added or removed, and “Write again” replaces the text with a new draft from the resume, job and tone you have chosen, discarding your edits on the page.

Two of Harvard’s rules are left for you to check. “Keep letters concise and factual, no more than a single page” fits both lengths the tool offers, but every paragraph you add counts toward that page. And “Don’t overuse the pronoun “I”” is a matter of reading: the letters are written in the first person by design, and no check counts how many sentences open with “I”.

What access the letter writer needs

Writing a cover letter needs a free account and a resume built in the builder. A visitor can try the resume builder itself before creating an account, including a few uses of its AI writing help, but the letter writer is not part of that, and downloading either document needs the free account. The free plan keeps one built resume and 3 cover letters; Premium keeps 50 letters. Each letter written, and each “Write again”, takes one request from the writing help’s daily limit. Current limits are listed under cover letters on our builder page, and pricing lists the plans.

The final check is meaning, not pattern matching

Two sentences of Maya’s draft came through untouched, and neither is quite right. “I keep maintenance running for 140 rental units” uses her number and her units, but her resume says she scheduled maintenance visits, which is a smaller claim. “I bring 5 years of experience in operations” passed because her dates span five years, yet her title was Office Coordinator, and whether that counts as operations is for her to say, not the tool. The guard works on numbers and names. Whether “running” claims more than “scheduling”, or which field a job title belongs to, is a question of meaning, and none of its rules asks it.

Finish with a reading pass. Put each sentence beside the resume line it came from and ask whether the letter says more. A cover letter can only be as accurate as the resume beneath it. Tailor Your Resume Without Inventing Experience starts with that evidence rather than the job’s keywords.