I need to write a letter and want an AI to help, but I don't want it to sound like a template.

Which AI tool for which letter

Every tool below can produce a letter. The differences are in what you have to set up and what you get back. Facts about other tools are from their own pages, read on 15 October 2026.

ChatGPT. A general assistant: you describe the letter and revise by asking. OpenAI's help page says custom instructions, which apply to all your chats, are on all plans, with up to 1,500 characters on the no-cost and Go tiers and 5,000 on Plus, Pro and the business plans. That is where you can tell it how you write. Good for: any letter, many rounds of changes. Watch for: ceremonial openings and details it fills in to sound complete.

Claude. Also a general assistant. Anthropic's help center describes account-wide “Instructions for Claude”, projects with their own instructions, and skills that can adjust tone and format based on your own writing. Good for: longer letters and careful edits of a draft you paste in. Watch for: the same added details; check every name and date.

Gemini. Google's assistant; its overview page says people use it to write compelling emails. Good for: quick drafts if you already work in Google's apps. Watch for: generic phrasing unless you give it specifics.

Letter generator sites. Mailmeteor's AI Letter Writer, for example, says it uses GPT models, takes one prompt box, needs no sign-up and lists English, French, Spanish and German among its languages. Good for: a quick one-off. Watch for: one-shot drafts with no editing pass and no memory of how you write.

HidenGPT. A writing engine with 17 formats: Anything for most letters, Email for letters sent as email, Career for cover letters and resignation letters. Each draft goes through a red pen that cuts stock AI phrases and flags flat rhythm, and a plan lets you save a voice from 2 to 5 samples. It does not promise anything about AI detectors; the aim is a letter you would put your name to.

Example: the same letter, template version and yours

Here is the example request above. A template-style draft tends to open like this:

“I hope this letter finds you well. I am writing to inform you of the passing of my beloved father and to kindly request your assistance in closing his account during this difficult time.”

Thirty-four words, and the bank still does not know the account number, the date or what you want done with the money.

The version built from your facts (about 80 words in the body):

“Harbor Savings Bank Re: Account ending 4471, Robert Lowell (deceased)

Dear Sir or Madam,

My father, Robert Lowell, died on August 30, 2026. I am the executor of his estate and enclose a certified copy of his death certificate and my letters of administration.

Please close checking account ending 4471, stop any automatic payments or transfers from it, and send the remaining balance by check payable to the Estate of Robert Lowell at the address below.

If you need anything else from me, I can be reached at [phone] or [email].

Sincerely, Emma Lowell, Executor [Address]

Enclosures: death certificate (certified copy), letters of administration”

The second one is shorter, answers every question a clerk would ask, and says what the writer actually needs.

Formal, personal and complaint letters: what changes

Formal letters (a bank, an insurer, a landlord, an office). Purpose in the first two sentences, account or reference numbers near the top, one request, a list of enclosures. Tone: Formal or Professional.

Personal letters (a thank-you, a condolence letter, a letter to a grandchild). There is no template to follow, which is why generic drafts read as hollow. Give the tool two or three real memories or specifics and say who will read it. Tone: Friendly or Heartfelt. A saved voice matters most here, because the reader knows how you talk.

Complaint letters (a company, a property manager, a service). Dated facts, what you already tried, one outcome and a date. Tone: Formal. Leave out threats you have not checked with someone who knows the law where you live.

Length, as a rule of thumb: a formal or complaint letter fits on one page, about 150 to 350 words. A personal letter can be any length, but the ones people keep are usually under a page.