ARD
Agentic Resource Discovery
A search engine for agent tools.
Reality check
Early. Hugging Face runs a public registry, but one independent check in June found that none of the named contributor companies served a catalog yet.
How it works
Today an AI assistant can only use the tools someone wired into it beforehand, like a phone that only runs its pre-installed apps. ARD flips that. A website publishes a small file at /.well-known/ard.json (".well-known" is just the web's agreed folder for files like this, the same idea as robots.txt) listing what it offers: an MCP server, an agent other agents can talk to, an API, a skill.
Separate "registries" collect these files and answer plain-language searches. Say your travel agent needs a live-weather tool it has never heard of: it asks a registry, gets a ranked list, checks who published each tool, and connects. A high ranking doesn't mean a tool is trustworthy; the spec keeps relevance and trust separate. Entries can include sample questions a real user would ask, which makes search work better.
Who's behind it
Google announced ARD on June 17, 2026. The current version is v0.91, a "Proposal" dated August 26, 2026, from authors at Google and Hugging Face plus R.V. Guha (the creator of RSS and Schema.org).
It tells agents to look for ard.json first and treats the older ai-catalog.json address as its predecessor. On July 9, 2026 the two formally split into a publishing format (ai-catalog) and a discovery format (ARD). The file name changed within a few months, so early tutorials already show the old address.