# Agentic Resource Discovery (ARD)

> Source: <https://specification.website/spec/agent-readiness/agentic-resource-discovery/>
> Published: 2026-06-19 00:00:00+00:00

# Agentic Resource Discovery (ARD)

Publish an AI Catalog at /.well-known/ai-catalog.json listing the agent capabilities your domain offers — MCP servers, A2A agents — so registries and agents can find and trust them from one fetch.

## What it is

Agentic Resource Discovery (ARD) is a draft discovery layer — not a runtime — that lets a domain advertise which agent capabilities it offers and how to verify them. It answers three questions for an agent: where the right capability lives, which one to use, and whether it is safe to connect. It builds on the **AI Catalog** standard, both developed under a Linux Foundation working group and published Apache 2.0.

The core is a manifest at `/.well-known/ai-catalog.json`

. Each `entries[]`

item has a URN `identifier`

, a `displayName`

, a `mediaType`

, and either an inline `data`

object or a `url`

pointing at the real artefact. The media types tie ARD to the rest of the agent-readiness graph:

`mediaType` | Points at |
|---|---|
`application/mcp-server-card+json` | An
|

`application/a2a-agent-card+json`

[A2A agent card](/spec/agent-readiness/a2a-agent-cards/)`application/ai-catalog+json`

Beyond the well-known file itself, three mechanisms point agents at it: a `<link rel="ai-catalog">`

(also emittable as an HTTP `Link`

header); an `Agentmap:`

directive in `robots.txt`

; and DNS service-binding records `_catalog._agents.<domain>`

and `_search._agents.<domain>`

— the same `_agents`

namespace as [DNS-AID](/spec/agent-readiness/dns-aid/).

## Why it matters

**One fetch, typed answer.** Instead of guessing at well-known paths one by one, an agent reads a single manifest that names every capability and its media type.**Domain-anchored trust.** An optional`trustManifest`

(SPIFFE ID, DID, or HTTPS identity, plus attestations and an optional JWS signature) lets a client verify the publisher cryptographically. The domain in the entry’s URN must align with the trust identity.**Registry-friendly.** Registries crawl published catalogs and make them searchable, so a capability listed once becomes discoverable across the agentic web.

## How to implement

Publish `/.well-known/ai-catalog.json`

with a `specVersion`

, a `host`

block, and one entry per capability you actually run. Reference your existing MCP and A2A cards by `url`

rather than duplicating them. Advertise the manifest with a `link rel`

, the `robots.txt`

`Agentmap:`

directive, and, if you publish DNS, the `_catalog._agents`

record. Don’t list endpoints you don’t offer.

This site ships it: [ /.well-known/ai-catalog.json](/.well-known/ai-catalog.json) catalogues our MCP server and A2A agent, advertised through the

`Link`

header, a `link rel`

, and `robots.txt`

.## Common mistakes

- Inventing fields. The entry schema is small —
`identifier`

,`displayName`

,`mediaType`

, and exactly one of`url`

or`data`

. - A URN publisher segment that doesn’t match the
`trustManifest`

identity domain — verification then fails. - Listing aspirational capabilities. The catalogue is a contract; only list what resolves.

## Verification

`curl -s https://example.com/.well-known/ai-catalog.json | jq .`

returns valid JSON with`specVersion`

and`entries`

.- Each entry
`url`

resolves to a document of the declared`mediaType`

. - The
`Agentmap:`

line is present in`robots.txt`

and the`ai-catalog`

`Link`

rel is on the homepage response.

## Related topics

## Sources & further reading

-
[Agentic Resource Discovery (ARD) specification](https://agenticresourcediscovery.org/)— ARD Project (Linux Foundation) -
[AI Catalog standard](https://github.com/Agent-Card/ai-catalog)— AI Catalog Working Group, Linux Foundation -
[RFC 8141 — Uniform Resource Names (URNs)](https://www.rfc-editor.org/rfc/rfc8141)— IETF -
[Announcing the Agentic Resource Discovery specification](https://developers.googleblog.com/announcing-the-agentic-resource-discovery-specification/)— Google