Interface for agents: Web design for agentic systems

The Invisible UI

For the first time in history, we are designing for users who do not have eyes. AI agents interact with websites through the DOM, metadata, and API endpoints. They do not see a layout; they read a structure. This creates the need for an "invisible UI" — a layer of the site designed specifically for machine consumption, running in parallel with the one humans read.

This guide sets out what that layer is, how to build it, and how to keep it from becoming the whole thing. Each section moves from the principle to the practical move a team can make to make their site legible to the agents that are increasingly the ones that find it.

Optimising for Agentic Discovery

Agentic discovery relies on semantic clarity. Using a clean DOM hierarchy and rich structured data (JSON-LD) allows an agent to find the most relevant information without having to "guess" based on visual cues. A site that is easy for an AI to parse is a site that will be recommended more often, because it is the one the agent can actually use.

The shift is subtle but profound. For twenty years, "findable" meant a human clicking a link on page two of Google results. Today, it increasingly means an agent choosing your content as the answer to a question it was asked by a human. The surface changes; the goal does not.

The Signals an Agent Reads

The signals that matter to a machine are the ones that a human usually does not notice: the order of the DOM, the names of the tags, the presence of structured data. Design those first, and the visual layer can be as expressive as you like.

• A DOM that mirrors the structure of your content

• Heading tags that describe meaning, not just size

• Structured data (JSON-LD) for the most important facts

• A clean, semantic HTML foundation

Making a Page Legible

• One clear topic per page

• A heading that names that topic

• Facts exposed as structured data, not just prose

• Links that describe their destination

The Dual-Experience Challenge

The challenge is to maintain a premium human experience while optimising for AI. We cannot simply build a site that looks like a directory of tags. The solution is to embed the machine-readable data deeply into the architecture, allowing the visual layer to remain an artistic expression for the human visitor.

The two layers are not the same layer. They are two views of the same content, and a good design makes both good. When a page is designed for a machine and it also happens to be good for a human, that is the highest form of the craft.

Embedding the Invisible UI

The practical move is to treat structured data as part of the design, not an add-on. It is not a separate task for an engineer; it is a property of how the content is built.

The Invisible UI in Practice

• Structured data that reflects the visual layout

• Headings that carry meaning into the machine layer

• An API surface that agents can call, not just an HTML page they can crawl

• Metadata that names the content for its purpose, not its title

Building Both Layers

The two-layer site is a design project, not an engineering task. It starts with a question about content: what does this page exist for? Answer that, and the machine layer and the human layer both follow.

1. A Practical Starting Point

Begin with your most important page, the one you most want an agent to recommend. Add structured data, clean the DOM, name your headings by meaning. Ship that one. Let the rest of the site follow the same template.

2. Keeping the Human Layer Premium

The temptation is to make the human layer the one that suffers. Resist it. The best version of the site is the one where both layers are excellent, and where no one in the room knows there are two layers. That is the sign of the craft.

Adoption Checklist

• Structured data on your most important page

• A clean, semantic DOM throughout

• Headings that carry meaning

• An API surface for agents, not just a crawlable HTML page

Conclusion

The web is becoming a database of intent. Those who design for both the eye and the agent will own the future of discovery. The invisible UI is not a lesser layer, and not a hidden one. It is the layer that, increasingly, decides whether a brand is found at all. Design it well, and your brand will be the one the agents choose, and the one the humans who receive the recommendation decide to visit.

Get in touch to discuss how we can help you build an "invisible UI" for your site, without sacrificing the experience your human visitors deserve.