How to Write Your First Prompt for an AI Agent (Without Coding)
Based on official prompting guidance from Anthropic and Google, consulted on 24 October 2026.
With a chatbot, a vague question costs you a vague answer. With an agent that opens files, browses sites and builds documents, a vague brief costs you time, and sometimes a mess to undo.
The good news: you don't need code. You need a clear brief.
Think "new colleague," not "search box"
Anthropic's prompting guide puts it this way: think of the AI "as a brilliant but new employee who lacks context on your norms and workflows. The more precisely you explain what you want, the better the result."
It also suggests a simple test. Show your prompt to a colleague with little context. "If they'd be confused, Claude will be too."
Google's Gemini help pages say something similar. Good instructions cover four areas: the role to play, the task, the context and the format you want.
The five-part brief
1. Goal: what "done" looks like
Say the result, not the activity. "Summarise my invoices" is an activity. "A table of every unpaid invoice from September, with client, amount and due date" is a result.
2. Context: why, and for whom
Anthropic notes that explaining the reason behind an instruction helps the model "deliver more targeted responses." Say who will read the result and what it's for.
3. Steps: when order matters
The same guide recommends giving "instructions as sequential steps using numbered lists" when order or completeness matters. Agents do multi-step work, so this is where you earn your result.
4. Format: exactly what to hand back
File type, columns, length, tone, where to save it. Be specific. Anthropic calls examples "one of the most reliable ways to steer" format and tone, so paste one if you have it.
5. Limits: what not to touch
This part matters most for agents. Say which folders it may use, what it must not delete or send, and when it should stop and ask you.
A ready-to-copy first prompt
Goal: Create a spreadsheet of unpaid invoices from September 2026.
Context: I'm a freelancer. I'll use this to send payment reminders on Friday.
Steps: 1) Open the PDFs in the "Invoices/2026-09" folder. 2) For each one, find client, invoice number, amount and due date. 3) Check the "Payments" sheet and leave out any invoice marked paid.
Format: One spreadsheet, one row per invoice, sorted by due date. Save it as "unpaid-september.xlsx" in the same folder.
Limits: Only use these two locations. Don't email anyone. Don't delete or rename files. If a PDF is unreadable, list it at the end instead of guessing.
Set the guardrails in the tool, too
Your prompt isn't the only control. In Claude Cowork, for example, Anthropic's help centre describes:
- Folder access: Claude reads and writes only in folders you've connected.
- Permission modes: Manual, Auto and Skip. For work involving money, messages sent as you or important files, Anthropic advises staying close or switching back to Manual.
- Deletion protection: Claude needs your explicit permission before permanently deleting files.
- Standing instructions: global instructions for every session, and folder instructions for a specific project.
If you repeat the same context every time, move it into those standing instructions and keep your prompt short.
Your first week
- Pick one boring, low-risk task.
- Write the five-part brief.
- Run it, then review every line of the result.
- Note what went wrong and add one sentence to the brief to prevent it.
- Run it again next week.
Go deeper
Our Portuguese-language book Agentes de IA para quem não programa (AI Agents for People Who Don't Program) turns this method into a full delegation plan, with everyday examples and honest limits.
👉 See our books at bookpilot.org/books
Sources
All consulted on 24 October 2026. Product details may have changed since.