# Agentic Resource Discovery ARD
[1 · Discover](/category/discover/)
| Agentic Resource Discovery |
| --- |
| Category | [Discover](/category/discover/) |
| Governed by | Authored by individuals at Google, Microsoft and Hugging Face (Junjie Bu, R.V. Guha, Shaun Smith); published as an open GitHub project (ards-project/ard-spec) with no formal standards body yet; contributions acknowledged from AWS, Cisco, Databricks, GitHub, GoDaddy, Nvidia, Salesforce and Snowflake |
| Status | Proposal |
| Phase | draft |
| Implementation | shipping |
| Adoption | observed — agenticresources.dev own probe, 2026-09-04 |
| Version | v0.91 (2026-08-26) |
| Specification | [https://raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md](https://raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md) |
| Found at | /.well-known/ard.json |
| Acronym collisions | ARDP (Agent Registration and Discovery Protocol, unrelated IETF draft), AIR (the urn:air: identifier namespace this spec defines is sometimes referred to standalone) |
| Last checked | 2026-09-06 |
[Discover](/category/discover/) Agentic Resource Discovery (ARD) is a specification for how agentic resources -- MCP servers, A2A agents, skills, and other callable services -- are described, discovered, and searched across a federated network of registries [[1]](#ref-1). It is authored by individuals at Google, Microsoft and Hugging Face and published as an open GitHub project (ards-project/ard-spec) rather than through a formal standards body; the current text is version v0.91, dated 26 August 2026, and is explicitly labelled a "Proposal" [[1]](#ref-1).
## Overview
ARD solves the problem of scaling tool selection beyond an LLM's context window: instead of injecting every possible tool description into a prompt, a client searches a registry's index using natural language plus structured filters, and the registry returns ranked entries [[1]](#ref-1). Each entry is a JSON-LD node with a small set of required terms (identifier, displayName, type, and either url or data), and publishers can extend it with arbitrary namespaced terms without waiting for a spec revision [[1]](#ref-1). Entries are advertised through a well-known manifest, robots.txt Agentmap directives, an HTML tag, DNS SVCB records, or in-page markup; the manifest path is /.well-known/ard.json [[1]](#ref-1).
A significant correction to earlier internal notes: the v0.91 text makes /.well-known/ard.json the canonical path and explicitly demotes the older /.well-known/ai-catalog.json path (and the ai-catalog link relation) to an optional predecessor that a conformant consumer is not required to consult [[1]](#ref-1). Prior assumptions that ai-catalog.json was still canonical as of this version are wrong as of the text fetched 2026-09-06.
ARD does not define a signing or authentication scheme of its own (it defers to whatever trust framework a publisher's trustManifest declares), does not constrain artifact-specific schemas (MCP, A2A, etc. remain external), and does not define a normative way to fetch a full entry by identifier from a search result [[1]](#ref-1).
Implementation exists: AGNTCY's Agent Directory Service explicitly serves /.well-known/ai-catalog.json and can export records into a2a, mcp, oasf and agent-skill formats, functioning as one real ARD-manifest-compatible implementation [[3]](#ref-3). Beyond that, adoption is thin and lagging the spec's own migration: a probe of 50 domains run by this site's publisher (agenticresources) on 2026-09-04 found 31 serving some manifest, all 31 still on the deprecated ai-catalog.json path, and only 6 of those also serving the new ard.json path [[4]](#ref-4) -- meaning the observed deployment base predates this very revision's path rename. Because that probe artifact is not present in this repository, adoption here is recorded as "observed" rather than "measured".
What is disputed or unknown: whether the ecosystem migrates to ard.json before a competing discovery mechanism (DNS-AID, AID, ADP) becomes the practical default; whether any registry beyond ADS has implemented the POST /search and POST /explore REST surface this spec mandates; and how the optional trustManifest verification step will be operationalized across publishers who have never coordinated on a trust framework.
The record ai-catalog-well-known-file, which previously modelled the manifest file as a separate entity, has been folded into this record: it described the same well-known artifact that this specification now supersedes with ard.json, and keeping it separate obscured that the two are one lineage, not two competing formats.
## Discovery and probe
well-known manifest, robots.txt Agentmap directive, HTML , DNS SVCB, in-page JSON-LD · /.well-known/ard.json
```
GET https://{origin}/.well-known/ard.json
parse: 200 response is JSON with a top-level "entries" array of ARD entries (each with identifier/displayName/type/url-or-data); a consumer MAY also check the predecessor /.well-known/ai-catalog.json and an HTML tag
on absent: Domain publishes no ARD manifest at the current canonical path; it may still publish at the deprecated predecessor path /.well-known/ai-catalog.json, which conformant consumers are not required to consult
```
Live check run by [the MCP probe](/mcp/server-card): GET /.well-known/ard.json. An ARD manifest is JSON with a top-level entries array.
```
{
"path": "/.well-known/ard.json",
"expect": {
"json_keys": [
"entries"
]
},
"note": "An ARD manifest is JSON with a top-level entries array."
}
```
## History
- 2026-09-05 — seeded from Exa Agent research run
- 2026-09-06 — verified against ARD v0.91 spec text (raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md); corrected canonical path from ai-catalog.json to ard.json; folded ai-catalog-well-known-file into this record
## Instances
- [agenticweb.wiki](https://agenticweb.wiki/.well-known/ard.json) · Observed 2026-09-06 · site
- [Hugging Face (ard/ai-catalog manifest at huggingface.co)](https://huggingface.co/.well-known/ai-catalog.json) · Observed 2026-09-04 · site
- [agenticresources.dev probe (31/50 domains serving a manifest, all on ai-catalog.json, 6 also on ard.json)](https://agenticresources.dev/) · Observed 2026-09-04 · site
- [AWS (Agent Registry / Bedrock AgentCore)](https://aws.amazon.com/blogs/machine-learning/agentic-resource-discovery-ard-an-open-specification-for-agent-discovery/) · Observed 2026-08-24 · business
- [Dries Buytaert (dri.es)](https://dri.es/helping-agents-discover-my-site-search-with-agentic-resource-discovery) · Observed 2026-07-23 · site
- [Databricks / GitHub / Salesforce / ServiceNow / Snowflake / Cisco / Nvidia (ARD launch backers)](https://qail.ai/agentic-resource-discovery-ai-catalog-json/) · Observed 2026-07-07 · network
- [AGNTCY Agent Directory Service (ai-catalog.json export/import)](https://datatracker.ietf.org/doc/html/draft-mp-agntcy-ads-02) · Observed 2026-07-06 · registry
- [skillsandagents.co](https://edakrong.com/skillsandagents-agentic-resource-discovery/) · Observed 2026-07-03 · site
- [Google (ai-catalog.json launch)](https://cloudandsre.com/blog/agentic-resource-discovery-ard/) · Observed 2026-07-02 · business
- [Hugging Face](https://huggingface.co/blog/agentic-resource-discovery-launch) · Observed 2026-06-17 · business
- [AGNTCY / Cisco Outshift (Directory over ARD)](https://blogs.agntcy.org/technical/2026/06/17/ai-catalog-over-directory.html) · Observed 2026-06-17 · registry
Every instance with its source is listed on the [instances page](/instances/).
Our probe: seen on 6 of 50 probed origins, last 2026-09-04. Probed origins are whoever was asked about, not a sample; the count is a floor.
## See also
- Component: [AI Catalog well-known file](/protocols/ai-catalog-well-known-file/)
- [MCP Server Card](/terms/server-card/)
- [Well-known URI](/terms/well-known/)
- [Agentmap directive](/terms/agentmap/)
- [Agentic web](/terms/agentic-web/)
- Not to be confused with: ARDP (Agent Registration and Discovery Protocol, unrelated IETF draft), AIR (the urn:air: identifier namespace this spec defines is sometimes referred to standalone)
## References
- ARD v0.91 (26 Aug 2026), authored by Google/Microsoft/Hugging Face individuals, defines the ARD entry as a JSON-LD node and moves the canonical manifest path to /.well-known/ard.json, explicitly naming /.well-known/ai-catalog.json as the deprecated predecessor path that consumers MAY but need not consult. — [https://raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md](https://raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md) (2026-08-26) VERIFIED
- Google announced the Agentic Resource Discovery Specification and directed publishers to a well-known catalog mechanism. — [https://developers.googleblog.com/en/announcing-the-agentic-resource-discovery-specification/](https://developers.googleblog.com/en/announcing-the-agentic-resource-discovery-specification/) (2026-06-17) REPORTED
- AGNTCY's Agent Directory Service (ADS) implements AI Catalog interoperability, serving /.well-known/ai-catalog.json and exporting records to a2a/mcp/oasf formats -- one real implementation of the ARD manifest side. — [https://datatracker.ietf.org/doc/html/draft-mp-agntcy-ads-02](https://datatracker.ietf.org/doc/html/draft-mp-agntcy-ads-02) (2026-07-06) VERIFIED
- A probe of 50 domains run by this site's publisher (agenticresources) on 2026-09-04 found 31 serving a manifest, all 31 on the predecessor ai-catalog.json path, and only 6 of those also on the new ard.json path -- i.e. the ecosystem has not yet moved to the canonical path this v0.91 revision defines. — [https://agenticresources.dev/](https://agenticresources.dev/) (2026-09-04) REPORTED
Disputed: The path this specification calls canonical has changed between revisions and prior internal notes got this backwards: v0.91 (26 Aug 2026) makes /.well-known/ard.json canonical and demotes /.well-known/ai-catalog.json to an optional, non-required-to-consult predecessor path. Our own probe (2026-09-04, prior to this verification) found the entire observed deployment base still on the old ai-catalog.json path, with only 6 of 31 also serving the new path -- so real-world adoption lags the spec text by at least one full path rename. Adoption level is left as "observed" rather than "measured" here because no probe-run artifact exists inside this repository (data/) to cite by filename; the probe that produced the 31/50 figure lives in the sibling agenticresources.dev project.
[JSON](/data/protocols/ard.json) · [Markdown](/protocols/ard/index.md)