Agent Use Interface

What is AUI?

AUI is a lightweight XML catalog, served at /.well-known/aui.xml, that describes URL-parameter-driven actions a site supports. Large sites can split full task definitions into optional detail files linked from the catalog. Things like searches, filters, form pre-fills, share intents, and configuration links.

The same file serves two audiences: agents parse the XML structure to understand available tasks and construct URLs, while humans can open it in a browser to review what an agent will have access to.

How It Works

1. Publish — A site serves aui.xml at /.well-known/aui.xml, describing its URL-driven tasks with typed parameters, constraints, and examples.
2. Discover — An LLM agent finds the file via the site's llms.txt or the well-known path.
3. Parse — The agent reads the XML to understand available tasks, parameter types, enum options, and validation rules.
4. Construct — Based on the user's intent, the agent selects a task and builds a URL: {origin}{base-path}?key=value&...
5. Present — The user receives a link that opens the right experience — on the web or in a native app via universal links.

For large sites with many tasks, AUI supports a catalog + detail pattern: the root aui.xml lists all tasks with lightweight summaries, while complex tasks link to separate detail files via an href attribute. Agents read the catalog first, judge relevance, then fetch only the details they need.

Example

A trimmed AUI document for an online store:

<aui xmlns="https://agentuseinterface.org/schema/0.1" version="0.1">
  <name>Example Shop</name>
  <origin>https://shop.example.com</origin>
  <description>An online electronics store.</description>
  <tasks>
    <task id="product-search">
      <name>Search Products</name>
      <description>Search the product catalog.</description>
      <base-path>/search</base-path>
      <parameters>
        <param name="q" type="string" required="true">
          <description>The search query.</description>
        </param>
        <param name="sort" type="enum">
          <description>How to sort results.</description>
          <options>
            <option value="relevance">Best match.</option>
            <option value="price_asc">Cheapest first.</option>
            <option value="rating">Highest rated.</option>
          </options>
        </param>
      </parameters>
    </task>
  </tasks>
</aui>

See the full example with three tasks, enum options, validation patterns, and intent-to-URL examples.

Schema

The AUI XML namespace is:

https://agentuseinterface.org/schema/0.1

A normative XML Schema Definition (XSD) is available for validation. Include it in your document:

<aui
  xmlns="https://agentuseinterface.org/schema/0.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://agentuseinterface.org/schema/0.1
    https://agentuseinterface.org/schema/0.1/aui.xsd"
  version="0.1">

Comparison

AUI is intentionally narrow. Here's how it relates to other specifications: