Give each client its own AI workspace (a Claude Project, a ChatGPT custom GPT or Project, or a Gemini Gem) with two things inside: short instructions that tell the AI how to work, and one client brief that tells it what is true about the client. Setup takes about 30 minutes per client, and every chat in that workspace starts already briefed.
Why one workspace per client
Without a workspace, every chat starts from zero, and whoever is typing decides what the AI knows about the client. A dedicated workspace fixes three problems at once:
No more re-briefing. The client's facts, voice and rules load automatically in every chat.
No leaks between clients. One client's offers and tone can't slip into another client's work when each lives in its own space.
One version for the whole team. When the account manager, the copywriter and the strategist use the same workspace, they get the same answers.
It is also the foundation for everything else in context engineering for agencies: you can't keep client context current if it doesn't live in one known place.
What goes in: instructions vs knowledge
Every AI workspace has two places to put context: instructions and knowledge files. Put the rules in the instructions and the facts in one knowledge file. Mixing them is the most common setup mistake, because facts buried in instructions are hard to find and update.
Instructions and knowledge compared
Aspect
Instructions
Knowledge (the client brief)
Holds
How the AI should work
What is true about the client
Examples
Use the brief as the source of truth; ask when a fact is missing; never use other clients' information
Copy these instructions and replace the bracketed names. They work in Claude, ChatGPT and Gemini.
Workspace instructions
You are working for [Agency name] on the account of [Client name].
Use the attached client brief as the source of truth for every fact about [Client name]: offers, prices, audience, claims, people and decisions.
If a fact you need is not in the brief, say so and ask. Never guess prices, offers, names, statistics or claims.
Write in [Client name]'s voice as described in the brief, and follow its Rules section over any general best practice.
Never use information about any other client.
If something I tell you contradicts the brief, or a fact in the brief looks outdated, point it out so the brief can be updated.
The last line matters most over time: it turns every chat into a chance to catch drift instead of hiding it.
How to set up a client workspace in 30 minutes
Write the client brief first. Fill the client.md template: facts from the client's website, plus what only your team knows. Give every fact a source and a date.
Create the workspace and name it consistently. For example, "Acme — Content" or "Acme — All services". Use the same name in every tool.
Paste the instructions. Use the template above, with the client's and your agency's names.
Add the brief as the only fact file. One file, not a folder of old decks. If your tool can link a live Google Doc, link it instead of uploading a copy.
Add a few examples of approved work. Two or three short pieces the client signed off on teach the voice better than adjectives. Label them as examples.
Share it with the account team. Everyone working on the client uses this workspace, not a private copy.
Test it with five questions. Current price, main offer, target customer, one sentence in the client's voice, latest decision. Fix the brief if any answer is wrong.
All three tools offer the same two places, instructions and knowledge, under different names. Pick the tool your team already uses; the method doesn't change.
Where instructions and the client brief go in each AI workspace
Workspace
Instructions go in
The brief goes in
Good to know
Claude Project
Project instructions
Project knowledge
A Google Doc added from Drive stays synced to its latest version, in private projects only (Anthropic)
ChatGPT custom GPT
Instructions
Knowledge files
Best when the whole team needs the same reusable assistant for a client
ChatGPT Project
Project instructions
Project files
Best when you also want the client's past chats grouped in one place
Gemini Gem
Instructions
Knowledge
Holds up to 10 files; a file added from Google Drive uses its most recent version (Google)
Checked against each vendor's help pages on . Google is replacing Gems with skills, starting with personal accounts in November 2026: what changes.
Whichever you choose, check two settings before adding client material: who the workspace is shared with, and whether your plan's data settings and your client contract allow the information you are uploading.
Naming, ownership and access
Small conventions keep ten or thirty client workspaces manageable. Agree on them once, write them in your agency's playbook, and apply them to every new client.
Name: "[Client] — [service or All]", identical across tools. Anyone should find the right workspace in seconds.
Owner: one named person per client, usually the account manager, responsible for the brief and the workspace.
Access: only the people working on the account. Freelancers get the brief file, not access to every client.
Version: the brief carries a version number and a "last verified" date at the top.
Agency rules: your house style and process rules (the agency layer) go in a short shared file reused in every workspace, so you update them in one place.
Common mistakes
Uploading everything. The full brand book, old pitch decks, last year's strategy. The AI can't tell current facts from retired ones. Start with one brief and a few approved examples.
Facts in the instructions. Prices and offers written into the instructions get forgotten there. Keep facts in the brief, where the weekly check happens.
One workspace for several clients. "Our SaaS clients" in one project guarantees mixed-up facts and voices.
Private copies. Each teammate builds their own version, and the client ends up with five different AI briefs.
No owner. Without a named owner, the workspace is accurate on day one and drifts from day two.
Skipping the test. Five questions take two minutes and catch most gaps before a client does.
FAQ
Should an agency use one Claude Project per client?
Yes. One project, custom GPT or Gem per client keeps facts and voice separate and gives the whole account team the same starting point.
Claude Project, custom GPT or Gemini Gem: which is best for client work?
The one your team already uses. All three combine instructions and knowledge files, and the setup method is the same. What matters more is one brief, one owner and a weekly check.
What should I put in a client's AI workspace?
Short instructions on how to work, one client brief with sourced and dated facts, and two or three examples of approved work.
What should the instructions say?
Treat the brief as the source of truth, ask instead of guessing, follow the client's voice and rules, never use other clients' information, and flag anything that looks outdated.
How long does it take to set up?
About 30 minutes per client if you start from a template, most of it spent filling the brief.
Can freelancers use the workspace?
Give freelancers the client brief file rather than access to your workspaces. They get the same facts without seeing other clients.
Start with a brief that stays current
The workspace is only as good as the brief inside it. SagaJoe builds that brief from each client's website, with a source on every fact, and re-checks it every week so you only approve what changed. See how it works.
