Fenwyx field guide
How to choose a
growth agency.
A practical evaluation framework for founders and growth leaders who need more than a persuasive pitch and a list of channels.
Short answer
Choose a growth agency that can diagnose the commercial constraint, connect its disciplines through one experiment system, define measurement before execution and show exactly who owns the work. The best partner makes decisions clearer and your internal team stronger.
01 / Framework
Five evidence tests for evaluating an agency
Use these tests during the first call, proposal review and reference conversation. They reveal how an agency thinks when the answer is uncertain, which is where most growth work lives.
Can they name the commercial problem?
A strong agency should translate channel symptoms into a business constraint. Listen for a clear distinction between what is known, what is assumed and what must be tested.
Do the disciplines share one learning loop?
Ask how media, creative, landing-page UX and lifecycle teams exchange evidence. Separate reports are not the same as a connected operating system.
Are experiment decisions defined in advance?
Good partners document the hypothesis, primary metric, guardrails, evidence threshold and next decision before launch. That prevents every result from being framed as a win.
Is senior ownership visible?
Confirm who diagnoses the problem, who does the work and who joins the weekly decisions. A polished pitch is less important than access to accountable expertise.
Will your team become more capable?
The engagement should improve your measurement, creative memory and decision quality. You should retain the evidence and operating knowledge, not just receive deliverables.
02 / Interview
Questions to ask before signing
- What do you believe is our most important growth constraint, and what evidence would change your mind?
- Which metric will define success, and which guardrails stop us from buying short-term growth at the expense of margin or retention?
- How many meaningful experiments can our team realistically support, and what will you need from us each week?
- Who will work on strategy, media, creative and conversion, and when will we speak with those people directly?
- What information, accounts, creative files and experiment history will we own if the engagement ends?
03 / Comparison
Growth agency versus channel agency
04 / Warning signs
Red flags to take seriously
Be cautious when an agency guarantees a specific result before seeing your economics and data, hides the delivery team, treats reporting as strategy, or recommends more spend before checking conversion and retention. Another warning sign is a proposal with many activities but no explanation of how decisions will change when the evidence changes.