Writing Effective Instructions

Supplying context gets the right material in front of Claude. Instructing well decides what Claude does with it. The gap between a mediocre answer and a partner-ready one is rarely the document; it is almost always the precision of the request. This page is the craft of that request.

Five parts of a good instruction

Strong instructions tend to carry the same five elements. You do not need a rigid template, but if an answer disappoints, one of these is usually missing.

• Role. Who is Claude helping, and from what seat? “You are assisting a private equity associate” sets the register and the depth.
• Task. The single thing you want done, stated plainly. One clear job beats three vague ones.
• Constraints. The boundaries: length, scope, what to include, what to leave out, which source to rely on.
• Format. The shape of the output: headings, a table, bullet points, a one-paragraph summary. Decide it; do not leave it to chance.
• What to do when unsure. The instruction most people forget. Tell Claude to ask, or to flag, rather than guess. This is what turns a confident-but-wrong machine into a careful one.

Before and after

The same task, instructed two ways. Notice that the second version is barely longer; it is just specific where the first is loose.

Building an instruction, step by step

When a task matters, assemble the request deliberately rather than typing the first thing that comes to mind.

1. Name the seat

   Open with the role so Claude pitches at the right level: “You are assisting a private equity associate screening Project Atlas, a mid-market field-service software target.”

2. State the one task

   Say the single thing you want, in plain words. If you have three jobs, consider three messages, or number them explicitly so none gets dropped.

3. Set the constraints

   Add the boundaries: how long, what to cover, what to ignore, and which source to trust. “Use only the attached files” keeps Claude from drifting into general knowledge.

4. Fix the format

   Choose the output shape: a table, four headings, five bullets, a single paragraph. A defined format is easier to read and far easier to verify.

5. Add the fallback

   Close with what to do when unsure: “Ask me if anything is ambiguous, and flag (do not fill) any gap in the source.” Now Claude surfaces uncertainty instead of hiding it.

A worked example

Here is the full shape assembled into one instruction you can adapt for almost any screening task.

You are assisting a private equity associate screening Project Atlas, a mid-market field-service software target. I have attached the teaser.
Task: produce a one-page initial screen.
Constraints: rely only on the attached document. Keep it to a single page. Cite the page number for any figure you quote.
Format: use these four headings, each with short bullets:

Business overview
Financial highlights
Investment angle
Key risks and open questions
When unsure: if the teaser does not state something, write “not stated” rather than estimating, and list anything ambiguous at the end as questions for management.

Every part is doing a job: the role sets depth, the task is singular, the constraints fence the answer, the format makes it usable, and the fallback turns silent guesses into a clean list of questions.

Custom styles and house tone

One instruction deserves its own treatment: how you want the answer to sound. Claude can write in almost any register, which is useful and also a trap. Left to its own defaults it tends toward the enthusiastic and the wordy, neither of which belongs in an investment committee paper. Tone is an instruction, not a hope. State it the same way you state the task and the format, and a few words is usually enough: “concise, neutral, no superlatives, US English” reshapes an answer completely.

The simplest way to control tone is to name it inside the request, alongside the role, task, and format you already specify.

You are drafting for a private equity audience. Write in our house voice throughout:

Concise and partner-ready: no filler, no throat-clearing introductions.
Neutral and measured: state findings plainly, avoid superlatives and hype.
Precise: prefer specific figures and clear caveats over vague positives.
US English spelling and conventions.
Now draft a three-paragraph summary of Project Atlas suitable for an initial investment committee read.

Pasting a tone block into every chat works, but it is repetitive and easy to vary by accident. For anything you do regularly, capture the voice once so it applies automatically. There are two clean ways to do this:

• A saved Style. Claude lets you capture a writing style and apply it to a conversation, so you select your house voice rather than retyping it. This is ideal for a personal, consistent register across one-off chats.
• Standing instructions in a Project. A Project holds instructions that apply to every conversation inside it. Put your house-voice block in the Project instructions and every memo, email, and summary you draft in that Project inherits the same tone without a single extra line. This is the better route for sustained deal work, because the voice and the deal context live together. See Instructions for Claude for how to write that standing block, the Projects section for the setup, and Instruction Templates for reusable starting points.

Specifying a measured, caveat-friendly voice does more than make prose look professional. A voice that prefers “the document states” over “this is a fantastic business” naturally surfaces the evidence and the gaps, which makes the output easier to verify. Hype hides uncertainty; a neutral register exposes it. The tone you ask for and the rigor you want tend to pull in the same direction.

The takeaway

Precise instructions are not longer or more complex; they simply leave nothing for Claude to invent. Name the seat, state one task, set the constraints, fix the format, and say what to do when unsure. When you find yourself typing the same instructions on every deal, capture them once as standing Instructions for Claude so they apply automatically, and lock a consistent voice at the same time using the house-tone approach in the section above. For the underlying anatomy of a prompt, see Anatomy of a Good Prompt.