Agentic Resource Discovery (ARD)

The Linux Foundation working group released the Agentic Resource Discovery (ARD) specification, a draft discovery layer that allows domains to advertise agent capabilities via a manifest at /.well-known/ai-catalog.json. ARD enables agents to find, select, and verify trusted MCP servers and A2A agents through a single fetch, with support for cryptographic trust verification and registry crawling.

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