Agency and Vendor Management: How to Get More from Your Partners

In my fifteen years as a marketing leader, I have seen the agency-client relationship from both sides of the table. I began my career on the agency side, at global networks like Publicis and Omnicom, crafting campaigns for some of the world’s biggest brands. For the past decade, I’ve been on the client side, hiring and managing agencies for companies like ING, P&G, and WeTransfer. This dual perspective has given me a unique understanding of what it takes to build successful, productive partnerships with external vendors.

As an interim CMO, I am often brought in to assess and optimize a company's marketing operations, and agency management is a critical piece of that puzzle. Effective agency management is more than just a procurement exercise; it is a strategic capability. When you engage an external partner, you are not just buying a service; you are investing in expertise, creativity, and an extension of your team. The right agency can be a powerful force multiplier, bringing fresh perspectives and specialized skills that you may not have in-house. However, the wrong partnership can lead to wasted budgets, missed deadlines, and endless frustration. The difference between success and failure often comes down to how you manage the relationship.

This article will provide a comprehensive guide to getting the most out of your agency and vendor partnerships. We will cover everything from writing effective briefs and setting clear Service Level Agreements (SLAs) to conducting productive performance reviews and structuring fees for mutual success. I will also share my perspective on when it makes sense to bring capabilities in-house versus outsourcing them. Whether you are a seasoned enterprise leader or a startup founder hiring a marketing team for the first time, this guide will provide you with the tools you need to build and maintain a high-performing network of external partners.

The Foundation: Briefing and Scoping

Every successful agency engagement begins with a clear and comprehensive brief. A well-crafted brief serves as the North Star for the project, aligning both your internal team and your external partner on the goals, deliverables, and constraints. A common mistake I have seen is providing a brief that is too vague or, conversely, too prescriptive. The ideal brief provides just enough information to inspire creative and strategic thinking without dictating the solution.

When I worked with Levi's, we developed a briefing template that became the standard for all our marketing initiatives. It included the following sections:

• Background and Business Context: Why are we doing this project? What is the business problem we are trying to solve?
• Objectives and Key Results (OKRs): What does success look like? How will we measure it? Be specific and quantitative wherever possible.
• Target Audience: Who are we trying to reach? What are their needs, motivations, and pain points?
• Key Message: What is the single most important thing we want to communicate?
• Mandatories and Constraints: What are the non-negotiables? This could include brand guidelines, legal requirements, or budget limitations.
• Deliverables: What are the specific outputs you expect from the agency?
• Timeline and Milestones: When do you need the deliverables? What are the key checkpoints along the way?

Taking the time to create a thorough brief will save you countless hours of rework and frustration down the line. It also forces you to clarify your own thinking and ensure that all internal stakeholders are aligned before you even approach an agency.

Setting the Rules of Engagement: SLAs and Performance Reviews

Once you have selected an agency and agreed on the scope of work, the next step is to formalize the rules of engagement. This is where Service Level Agreements (SLAs) come in. An SLA is a contractual agreement that defines the level of service you expect from your agency, including metrics for performance, response times, and reporting.

SLAs should be specific, measurable, achievable, relevant, and time-bound (SMART). For example, an SLA for a performance marketing agency might include targets for cost per acquisition (CPA), return on ad spend (ROAS), and click-through rate (CTR). For a creative agency, you might have SLAs around turnaround times for new concepts or rounds of revisions.

Regular performance reviews are essential for ensuring that your agency is meeting the agreed-upon SLAs and delivering value. I recommend a quarterly business review (QBR) process, where you sit down with your agency partners to review performance against goals, discuss what is working and what is not, and plan for the quarter ahead. These reviews should be a two-way conversation, providing an opportunity for the agency to share feedback and suggestions as well. The outputs of these reviews should be concise and clear enough to be included in board-level reporting.

The Money Talk: Fee Structures and Incentives

There are several common models for structuring agency fees, each with its own pros and cons:

• Retainer: A fixed monthly fee for a defined scope of work. This model provides predictability for both the client and the agency, but it can be inflexible if your needs change.
• Project-Based: A fixed fee for a specific project. This is a good option for one-off initiatives, but it can be less cost-effective for ongoing work.
• Commission-Based: The agency earns a percentage of media spend or revenue generated. This model aligns the agency's incentives with your business goals, but it can be difficult to track and attribute accurately.
• Value-Based: The agency's fee is based on the value they deliver to your business. This is the most difficult model to implement, but it can also be the most rewarding for both parties.

In my experience, a hybrid model that combines a retainer for ongoing work with project-based fees for specific initiatives often works best. I am also a strong believer in performance-based incentives. When I was at ING, we implemented a bonus structure for our media agency that was tied to key business metrics like brand awareness and customer acquisition. This created a true partnership, where the agency was motivated to think beyond their immediate scope of work and contribute to our overall business success.

The In-House vs. Outsource Dilemma

One of the most common questions I get from clients is whether they should build a particular capability in-house or outsource it to an agency. There is no one-size-fits-all answer; the right choice depends on your specific needs, resources, and long-term goals.

Here are a few factors to consider:

• Cost: Building an in-house team requires a significant upfront investment in salaries, benefits, and overhead. Outsourcing can be more cost-effective, especially for specialized skills that you may not need on a full-time basis.
• Expertise: Agencies have a depth and breadth of expertise that can be difficult to replicate in-house. They work with multiple clients across different industries, which gives them a unique perspective on best practices and emerging trends.
• Scalability: Agencies can scale their resources up or down as your needs change. This can be a major advantage for businesses with fluctuating workloads or seasonal demand.
• Control: An in-house team gives you more control over your marketing activities and brand message. However, it can also lead to a more insular culture and a lack of fresh ideas.

At WeTransfer, we had a hybrid model that worked very well. We had a small in-house team of marketing generalists who were responsible for strategy, planning, and project management. We then outsourced specialized functions like performance marketing, public relations, and creative production to a network of trusted agency partners. This allowed us to maintain control over our brand and strategy while leveraging the expertise and scalability of our external partners. It also allowed us to build a flexible and powerful MarTech stack by integrating the tools and platforms our agency partners specialized in.

Conclusion: From Vendor to Partner

The key to successful agency and vendor management is to move beyond a transactional relationship and build a true partnership. This requires a foundation of trust, transparency, and mutual respect. When you treat your agencies as an extension of your team, you unlock their full potential and create a powerful engine for growth.

By following the best practices outlined in this article—from writing clear briefs and setting SMART SLAs to structuring fees for mutual success—you can build a high-performing network of external partners that will help you achieve your business goals. And if you need help navigating the complexities of agency and vendor management, you can always apply to work with me or check out my pricing.

Frequently Asked Questions (FAQ)

What is the most important factor in a successful client-agency relationship?

While many factors contribute to a successful partnership, the most important is clear and consistent communication. This includes providing a detailed brief, setting clear expectations and SLAs, and conducting regular performance reviews. When both parties are aligned and communicating openly, it is much easier to navigate challenges and achieve shared goals.

How do you measure the ROI of an agency partnership?

The ROI of an agency partnership should be measured against the specific goals and objectives outlined in your brief and SLAs. For a performance marketing agency, this might be metrics like ROAS or CPA. For a creative or brand agency, you might look at metrics like brand awareness, share of voice, or customer sentiment. It is important to have a clear marketing attribution model in place to accurately track the impact of your agency's work (Wikidata). [1]

When should a company consider bringing marketing functions in-house?

A company should consider bringing marketing functions in-house when they have a consistent, long-term need for a particular skill set and the resources to build and manage an internal team. Functions that are core to your brand identity and customer experience are often good candidates for in-housing. However, it is important to weigh the costs and benefits carefully, as outsourcing can provide greater flexibility and access to specialized expertise.

References

[1] J.P. Morgan. (2025). Vendor Management Guide: Tips & Strategies for Success. [2] McKinsey & Company. (2023). Marketing Organization and Operations.