How to Write the Perfect Agency Brief (Without Overthinking It)
Writing an agency brief should be one of the easier parts of the job. You know what you need, you put it in a document, the agency responds.
But in reality, it’s rarely that clean.
Often the challenge isn’t figuring out what the work is , it’s getting everyone aligned on what success looks like. You’re trying to reflect multiple stakeholder opinions, make the brief specific enough to be useful, and still leave room for the agency to bring thinking you haven’t considered yet. That balancing act alone can make even simple projects hard to brief well.
Then there’s the pressure of committing too early. Putting budgets, timelines or deliverables in writing can feel like locking yourself into decisions that might change. So the brief stays deliberately open… and the agency ends up making assumptions on your behalf.
Add in the fact that words like “strategy”, “brand refresh”, or “campaign” can mean very different things depending on who you ask, and it’s easy to see why briefs sometimes miss the mark.
And when the trade-offs haven’t been agreed, speed versus quality, ambition versus budget, testing versus certainty. You’ll get proposals that pull in completely different directions.
The good news? A strong brief doesn’t need to cover everything. It just needs to remove the uncertainty that matters most, so agencies can respond clearly, and you can choose with confidence.
First, let’s redefine what “perfect” actually means
A perfect brief isn’t:
A 20-page document
A locked-down solution
A test of how strategic you are
It is:
A clear articulation of the problem you’re trying to solve
An honest view of what you know — and what you don’t
A solid starting point for collaboration
Think of your brief less as a set of instructions, and more as an invitation. Its job is to help the right agency lean in, ask better questions, and do their best thinking.
The six things agencies really need from your brief
You don’t need to cover everything. But if you can get these six areas right, you’ll already be ahead of most briefs agencies see.
1. The real problem you’re trying to solve
“New website”, “app redesign” or “brand refresh” are rarely the actual problem — they’re the output.
What’s not working right now?
Is performance flat?
Are users confused?
Has the business outgrown the platform?
Is the brand no longer reflecting who you are?
Context here matters more than polish. Agencies can design solutions — but only if they understand the why behind the work.
2. What success looks like (in practical terms)
You don’t need a perfect KPI framework, but you do need a sense of what better means.
Ask yourself:
What would make you say this project was worth it?
What should be different six months after launch?
Who internally will judge whether this worked?
This helps agencies prioritise what matters, rather than guessing what you’ll be held accountable for later.
3. Who the work is for (and who it isn’t)
You don’t need personas or research decks, the agencies will do this, but you do need direction.
Who are you trying to reach?
Existing customers or new ones?
A broad audience or a specific segment?
Decision-makers, influencers, users, or buyers?
Equally useful is clarity on who this isn’t for. Boundaries help agencies focus their thinking instead of hedging.
4. Context, constraints and reality
This is the part many briefs shy away from, but agencies actually value most.
Things like:
Timelines that matter (and why)
Internal stakeholders or decision-makers
Technical constraints or legacy systems
Past attempts that didn’t quite land
None of this weakens your brief. It strengthens it. The more real-world context you share, the more realistic and useful the response will be.
5. What’s fixed, and what’s flexible
Ambiguity around constraints is one of the biggest causes of frustration on both sides.
Be as clear as you can about:
Budget range (even a ballpark)
Non-negotiables
Areas where you’re open to challenge or ideas
This doesn’t limit creativity, it directs it. Agencies can only propose smart solutions if they know where the lines are.
6. How you want to work together
This is often overlooked, but it sets the tone for the entire relationship.
Useful things to include:
Who the main point of contact will be
How decisions will be made
Preferred ways of working (hands-on vs hands-off, fast vs considered)
Any expectations around collaboration
You’re not just buying an output. You’re entering a working partnership, and the brief is the first signal of what that partnership might feel like.
Common briefing mistakes (that are completely normal)
If any of these sound familiar, you’re not doing it wrong, you’re just looking at it from the wrong angle.
Trying to define the solution before the problem is clear
Holding back budget to “see what comes back”
Briefing multiple projects in one document
Writing for procurement, not people
Most of these come from pressure or caution, not poor intent. The fix is usually clarity, not more detail.
What a good brief unlocks
When a brief is clear in the right places, something shifts. You see more aligned proposals, better and more considered questions from agencies, thinking that constructively challenges assumptions, and a stronger foundation for the work that follows. Most importantly, clarity helps attract agencies who actively want to work with you, because they understand the problem you are trying to solve and can clearly see where they will add value.
If you’re about to start an agency search and want support finding the right fit, our free Matchmaking service can help. We take the time to understand your brief, your constraints and what good looks like for your business, then connect you with agencies that are genuinely well suited to deliver.
It’s a simple, no-obligation way to remove friction from the process and start your next project with confidence.
