As product designers, part of our responsibility is shaping the interaction layer of our products, the parts users directly engage with on the screen. This includes interfaces, flows, and behaviors that define how people experience what we build. But in the age of AI, a new type of "user" is becoming increasingly important: agents.
What is an API?
An API (Application Programming Interface) is a way for different systems to communicate with each other. Instead of relying on a person to click buttons or fill out forms, one system can send a request to another to perform an action or retrieve information. User interfaces work through APIs. When someone submits a form or loads data, the UI sends a request to an API endpoint to make it happen.
APIs as an Accessibility Layer
Agents interact with your product via APIs. Like human users, they require clear, predictable, and well-designed experiences. From an interaction design perspective, this is a new type of audience, an invisible one that deserves thoughtful consideration and empathy.
APIs were once seen strictly as engineering territory, hidden infrastructure that designers rarely touched. But that boundary no longer holds. Today, APIs are how your product communicates with the intelligent world. That communication needs to be consistent, usable, and aligned with your product's experience goals.
In this light, APIs are what we might call the invisible UI. Like any interaction surface, APIs should be usable, consistent, and accessible. Designers need to understand what's being exposed and how those interactions embody principles of good design.
This shift isn't just about technical fluency. It's about ensuring usability for a broader spectrum of interactions. While accessibility often refers to inclusive design for people with different needs, designing for agents is a similar challenge, making sure systems can understand, access, and navigate your product's capabilities effectively. APIs become another touchpoint, and they should be just as thoughtfully designed.
Looking Ahead: Designing with Agents in Mind
Designing for agents means shifting our perspective. Instead of focusing solely on human interaction, we ask: how would a system initiate this task? What data does it need? What would a clear, reliable response look like?
APIs are no longer a technical detail; they are part of the product's interaction surface. They shape how experiences scale and adapt beyond the visible.
If we care about the people using our products, we must also care about the agents acting on their behalf. This shift challenges us to expand our definition of design and shaping the product's behaviour beyond what's visible on the screen.
If we approach APIs with the same empathy and intentionality we bring to interfaces, we can architect more adaptive, intelligent ecosystems.