Wordcraft

A writing skill for AI agents. It makes the emails, messages, summaries and reports your agent writes clearer and easier to read, whether you're reading them yourself or building agents that write for other people. It installs on Claude Code, Codex, Cursor, Gemini CLI and other agents that support skills.

npx skills add cz4000/wordcraft -g

Then add the always-on lines to your agent's instructions file. More install options.

Why I built it

I use Claude Code every day, and I'd grown tired of reading what it wrote. Short questions got long answers. End-of-session summaries listed every function it had touched, with names I'd never seen and nothing about what any of it meant for me. Emails it drafted could have come from anyone. The information was usually there, but getting it out was work.

In October 2026, Tim O'Reilly published a piece that Claude wrote and he only lightly edited, and it read beautifully. So Claude can write well. Then, on X, @samsonfraser suggested turning William Zinsser's On Writing Well into a skill. That's where Wordcraft started.

What's in it

Wordcraft starts from Zinsser and adds what testing showed was still missing.

• Zinsser's core. Cut clutter, write for a reader who knows nothing of your work, start with the one fact they need, sound like a person, and stop when you're done.
• Orwell's six rules. The short word over the long one, the everyday word over jargon, and cut any word you can.
• Euchner's ten rules. One idea per paragraph, and a complex subject taken one piece at a time.
• BLUF and SBAR. End-of-task summaries lead with the outcome, then cover what changed, what you need to do, what couldn't be checked and what's left behind.
• Plain words first. A name you haven't seen comes after a plain description, in brackets (like_this).
• Check before sending. When the material has a problem you'd want caught, such as a wrong date, figures that don't add up or a missing detail, the agent lists it after the draft.
• A note for each kind of writing. Summaries, emails, status updates, chat answers and longer pieces each get their own guidance.

It's two files, plus a few lines for your agent's instructions file so everyday chat answers follow the same rules.

Before and after

[!TIP] Clearer, and shorter. In blind tests on fresh writing tasks, judges preferred Opus 5.5 with Wordcraft in about 7 of every 10 comparisons that weren't ties. Its replies used 5–8% fewer words and 7–37% fewer output tokens than Opus 5.5 alone. Loading the skill adds some input tokens, most of them cached.

Negotiating a job offer

The request:

Got the offer through for the Brindlemoor job and it's lower than I was hoping. I do really want this one though, and I don't want to come across as greedy or blow it. Can you write my reply to Lena? Her email and my notes are below.

Opus 5.5 (517 words)

Here's a draft. It's warm and clearly keen, and it makes two asks.

---

Subject: Re: Offer – Senior Insight Analyst

Hi Lena,

Thank you so much, and thank you for being so helpful throughout the process. I really enjoyed meeting Graham and Sanjeev, and I'm delighted the arrears case study went down well. I'm very excited about this role and the team, and I'd love to make it work.

Before I accept, I'd like to discuss two points:

Salary: I was hoping for a base nearer the top of the advertised £48–56k range. I have seven years' experience, I led the Power BI migration at Kestrel, and I currently line-manage two junior analysts, so I think I'd bring a lot from day one. Would Brindlemoor be able to offer £56,000?

Office days: Graham mentioned in the interview that most of the team work two days in the office. Could this role be on the same pattern? It would make a real difference to me, as the commute is around 50 minutes each way.

Everything else looks great. The pension is very generous, and 1 December works well with my one-month notice period.

I know Graham wants to move quickly, so I'm happy to jump on a call whenever suits you this week if that's easier.

Thanks again, I'm really looking forward to hearing back.

Best wishes, Ruth

---

Why I wrote it this way:

• It asks for £56k because that's what you want. If they meet you halfway, you're at about £54k, which is the number you'd take. Your 7 years, the migration and managing two people make the top of the band easy to justify, and that's the only argument the email makes.
• The office-days ask uses Graham's own words. That makes it a question about fairness rather than a demand. I left the parking cost out because it reads as a complaint. If they push back, you can bring it up on a call as the reason the extra day matters.
• It doesn't mention annual leave. Three asks start to look like a list. I'd keep the 27 days for later: if they say they can't go higher on salary, you can ask, "Could you look at 27 days' leave instead?" It's an easy thing for them to give, and you can point out it's what you have now.
• It doesn't mention Calvert, Mags's salary, or what you said on the first call. You don't want to bluff about Calvert. Quoting a friend's salary can feel awkward to the person reading it. And since you can't remember whether you said "low to mid fifties" or 55, it's safer not to mention it. If Lena brings it up, "mid fifties" fits £56k.
• Your walk-away number of £52.5k isn't in the email. Asking for more isn't greedy, especially when you're saying you want the job. Companies expect a counter, and offering to call shows you'll be easy to deal with.

This is the beginning of the README. Read the rest at the original. Read the full README ↗